API Reference

SciTeX Stats - Publication-ready statistical testing framework.

Three Interfaces:

• Python API: import scitex_stats as ss

• CLI: scitex-stats <command>

• MCP: 10 tools for AI agents

Modules:

• tests: 23 statistical tests (parametric, nonparametric, correlation, categorical, normality)

• effect_sizes: Cohen’s d, Cliff’s delta, eta squared, epsilon squared, probability of superiority

• correct: Multiple comparison corrections (Bonferroni, FDR, Holm, Sidak)

• posthoc: Post-hoc tests (Tukey HSD, Dunnett, Games-Howell)

• power: Statistical power analysis and sample size calculation

• descriptive: Descriptive statistics and confidence intervals

• auto: Automatic test recommendation

scitex_stats.run_test(test_name, data=None, data2=None, groups=None, alternative='two-sided', plot=False, popmean=0, return_as='dict', json_safe=True, **kwargs)

Run a statistical test by name and return a normalised result dict.

Parameters:

• test_name (str) – Name of the test (e.g. "ttest_ind", "anova"). See available_tests() for the full list including aliases.

• data (array-like, optional) – Primary data array.

• data2 (array-like, optional) – Second data array (for two-sample / paired tests).

• groups (list of array-like, optional) – List of group arrays (for ANOVA, Kruskal, etc.).

• alternative (str, default "two-sided") – Alternative hypothesis for applicable tests.

• plot (bool, default False) – Whether to generate a plot.

• popmean (float, default 0) – Population mean for one-sample t-test.

• return_as (str, default "dict") – Passed through to the underlying test function.

• json_safe (bool, default True) – If True, apply to_json_safe() to the result.

• **kwargs (Any) – Additional keyword arguments forwarded to the test function.

Returns:

Test result dictionary. When json_safe is True, all numpy scalars are converted to Python types and a formatted key is added.

Return type:

dict

Raises:

ValueError – If test_name is not recognised.

scitex_stats.available_tests()

Return sorted list of canonical test names accepted by run_test.

Returns:

Accepted test name strings (including aliases).

Return type:

list of str

scitex_stats.describe(x, axis=-1, dim=None, keepdims=False, funcs=None, device=None, batch_size=-1)

Compute descriptive statistics.

Parameters:

• x (array-like) – Input data (numpy array or torch tensor)

• axis (int, default=-1) – Deprecated. Use dim instead

• dim (int or tuple of ints, optional) – Dimension(s) along which to compute statistics

• keepdims (bool, default=False) – Whether to keep reduced dimensions

• funcs (list of str or "all", optional) – Statistical functions to compute. Clean names (mean, std, median, etc.) use nan-safe implementations. Legacy nan-prefixed names (nanmean, nanstd, etc.) are also accepted. If None, uses default: [“mean”, “std”, “kurtosis”, “skewness”, “q25”, “median”, “q75”].

• device (optional) – Device for torch tensors (ignored for numpy)

• batch_size (int, default=-1) – Batch size for processing (currently unused)

Returns:

Computed statistics stacked along last dimension and their names

Return type:

Tuple[ndarray or Tensor, List[str]]

scitex_stats.to_json_safe(result)

Convert a test result dict to JSON-serializable Python types.

Handles numpy scalar/array conversion, inf/nan to None, key aliases for common frontend expectations, and builds a formatted summary string.

Parameters:

result (dict) – Raw test result dictionary from any stx.stats.test_*() function.

Returns:

JSON-safe dict with consistent keys and a formatted summary.

Return type:

dict

Examples

>>> import numpy as np
>>> raw = {"pvalue": np.float64(0.023), "statistic": np.float64(2.45),
...        "stat_symbol": "t", "effect_size": np.float64(0.85),
...        "effect_size_metric": "Cohen's d", "stars": "*"}
>>> safe = to_json_safe(raw)
>>> type(safe["pvalue"])
<class 'float'>
>>> "p_value" in safe
True
>>> "formatted" in safe
True

class scitex_stats.StatContext(n_groups, sample_sizes, outcome_type, design, paired=None, has_control_group=False, n_factors=1, normality_ok=None, variance_homogeneity_ok=None, missing_allowed=False, group_names=None, control_group_name=None)

Bases: object

Statistical context for determining which tests are applicable.

This dataclass captures all the information needed to decide which statistical tests can be applied to the current data/figure context. It is used by check_applicable() to filter the test registry.

Parameters:

• n_groups (int) – Number of groups/levels to compare (e.g., 2 for A vs B).

• sample_sizes (list of int) – Sample sizes per group in the same order as the groups.

• outcome_type (OutcomeType) – Type of outcome variable: - “continuous”: numeric, interval/ratio scale - “ordinal”: ordered categories, ranks - “binary”: 0/1 or yes/no - “categorical”: nominal with >= 2 categories

• design (DesignType) – Overall experimental design: - “between”: independent groups - “within”: repeated measures / paired - “mixed”: mixed design (some within, some between)

• paired (bool or None) – Whether the comparison is explicitly paired. If None, inferred from design.

• has_control_group (bool) – Whether a control group is identifiable (for Dunnett etc.).

• n_factors (int) – Number of factors; 1 for one-way, 2 for two-way, etc.

• normality_ok (bool or None) – Result of normality check if available. True = normal, False = non-normal, None = unknown.

• variance_homogeneity_ok (bool or None) – Result of homogeneity test (e.g., Levene). True = homogeneous, False = heteroscedastic, None = unknown.

• missing_allowed (bool) – Whether missing data is allowed for the chosen method.

• group_names (list of str, optional) – Names of the groups for display purposes.

• control_group_name (str, optional) – Name of the control group if has_control_group is True.

Examples

>>> # Two-group independent comparison
>>> ctx = StatContext(
...     n_groups=2,
...     sample_sizes=[30, 32],
...     outcome_type="continuous",
...     design="between",
...     paired=False,
...     has_control_group=False,
...     n_factors=1
... )

>>> # Three-group repeated measures
>>> ctx = StatContext(
...     n_groups=3,
...     sample_sizes=[20, 20, 20],
...     outcome_type="continuous",
...     design="within",
...     paired=True,
...     has_control_group=True,
...     n_factors=1,
...     control_group_name="baseline"
... )

>>> # Check if data appears normal
>>> ctx.normality_ok = True
>>> ctx.variance_homogeneity_ok = True

__init__(n_groups, sample_sizes, outcome_type, design, paired=None, has_control_group=False, n_factors=1, normality_ok=None, variance_homogeneity_ok=None, missing_allowed=False, group_names=None, control_group_name=None)

__post_init__()

Validate and set defaults.

control_group_name: Optional[str] = None

property effective_paired: bool | None

Effective paired status, considering design.

Returns:

True if paired/within, False if unpaired/between, None if unknown.

Return type:

bool or None

classmethod from_data(y, group, design='between', outcome_type=None, **kwargs)

Create StatContext from data arrays.

Parameters:

• y (np.ndarray) – Outcome values.

• group (np.ndarray) – Group labels for each observation.

• design (DesignType) – Experimental design.

• outcome_type (OutcomeType, optional) – Type of outcome. If None, inferred from data.

• **kwargs – Additional arguments for StatContext.

Returns:

Context built from the data.

Return type:

StatContext

Examples

>>> y = np.array([1, 2, 3, 4, 5, 6])
>>> group = np.array(['A', 'A', 'A', 'B', 'B', 'B'])
>>> ctx = StatContext.from_data(y, group)
>>> ctx.n_groups
2

classmethod from_dict(data)

Create from dictionary.

Return type:

StatContext

group_names: Optional[List[str]] = None

has_control_group: bool = False

property min_n_per_group: int

Minimum sample size per group.

missing_allowed: bool = False

n_factors: int = 1

property n_total: int

Total sample size across all groups.

normality_ok: Optional[bool] = None

paired: Optional[bool] = None

to_dict()

Convert to dictionary for JSON serialization.

Return type:

Dict[str, Any]

variance_homogeneity_ok: Optional[bool] = None

n_groups: int

sample_sizes: List[int]

outcome_type: Literal['continuous', 'ordinal', 'binary', 'categorical']

design: Literal['between', 'within', 'mixed']

class scitex_stats.TestRule(name, family, min_groups, max_groups, outcome_types, supports_paired, supports_unpaired, design_allowed, requires_control_group, min_n_total, min_n_per_group, needs_normality, needs_equal_variance, min_factors, max_factors, priority=0, description='')

Bases: object

Applicability rule for a specific statistical test.

Each TestRule defines the conditions under which a test is applicable. The check_applicable() function uses these rules to filter tests for a given StatContext.

Parameters:

• name (str) – Internal name of the test (e.g., “ttest_ind”, “brunner_munzel”).

• family (TestFamily) – High-level family of the test: - “parametric”: t-test, ANOVA, etc. - “nonparametric”: Mann-Whitney, Kruskal-Wallis, etc. - “categorical”: Chi-square, Fisher’s exact, etc. - “correlation”: Pearson, Spearman, etc. - “normality”: Shapiro-Wilk, etc. - “effect_size”: Cohen’s d, eta-squared, etc. - “posthoc”: Tukey, Dunnett, etc. - “other”: Other tests (Levene, etc.)

• min_groups (int) – Minimum required number of groups.

• max_groups (int or None) – Maximum allowed number of groups. None means no upper bound.

• outcome_types (set of str) – Allowed outcome types for this test.

• supports_paired (bool) – Whether the test supports paired/repeated measures.

• supports_unpaired (bool) – Whether the test supports independent groups.

• design_allowed (set of str) – Allowed designs, e.g., {“between”, “within”}.

• requires_control_group (bool) – Whether a dedicated control group is required (e.g., Dunnett).

• min_n_total (int or None) – Minimum total sample size. None means no constraint.

• min_n_per_group (int or None) – Minimum sample size per group.

• needs_normality (bool) – Whether test assumes normality (check normality_ok).

• needs_equal_variance (bool) – Whether test assumes equal variances (check variance_homogeneity_ok).

• min_factors (int or None) – Minimum number of factors.

• max_factors (int or None) – Maximum number of factors.

• priority (int) – Priority score for recommendation. Higher = more recommended. Brunner-Munzel has priority 110 as the recommended default for 2 groups.

• description (str) – Human-readable description for tooltips.

Examples

>>> rule = TestRule(
...     name="ttest_ind",
...     family="parametric",
...     min_groups=2,
...     max_groups=2,
...     outcome_types={"continuous"},
...     supports_paired=False,
...     supports_unpaired=True,
...     design_allowed={"between"},
...     requires_control_group=False,
...     min_n_total=4,
...     min_n_per_group=2,
...     needs_normality=True,
...     needs_equal_variance=False,
...     min_factors=1,
...     max_factors=1,
...     priority=90,
...     description="Independent samples t-test (Welch)"
... )

__init__(name, family, min_groups, max_groups, outcome_types, supports_paired, supports_unpaired, design_allowed, requires_control_group, min_n_total, min_n_per_group, needs_normality, needs_equal_variance, min_factors, max_factors, priority=0, description='')

description: str = ''

priority: int = 0

name: str

family: Literal['parametric', 'nonparametric', 'categorical', 'correlation', 'normality', 'effect_size', 'posthoc', 'other']

min_groups: int

max_groups: Optional[int]

outcome_types: Set[str]

supports_paired: bool

supports_unpaired: bool

design_allowed: Set[str]

requires_control_group: bool

min_n_total: Optional[int]

min_n_per_group: Optional[int]

needs_normality: bool

needs_equal_variance: bool

min_factors: Optional[int]

max_factors: Optional[int]

class scitex_stats.StatStyle(id, label, target, stat_symbol_format=<factory>, p_format='p = {p:.3f}', alpha_thresholds=<factory>, effect_label_format=<factory>, n_format='n_{%s} = %d', decimal_places_p=3, decimal_places_stat=2, decimal_places_effect=2)

Bases: object

Style configuration for statistical reporting.

Defines how to format statistical results for a specific journal or output format.

Parameters:

• id (str) – Unique identifier for this style.

• label (str) – Human-readable label (e.g., “APA (LaTeX)”).

• target (OutputTarget) – Output format: “latex”, “html”, or “plain”.

• stat_symbol_format (dict) – Maps statistic symbols to their formatted versions.

• p_format (str) – Format string for p-values.

• alpha_thresholds (list of (float, str)) – P-value thresholds for stars.

• effect_label_format (dict) – Maps effect size names to their formatted labels.

• n_format (str) – Format string for sample sizes.

• decimal_places_p (int) – Decimal places for p-values.

• decimal_places_stat (int) – Decimal places for test statistics.

• decimal_places_effect (int) – Decimal places for effect sizes.

__init__(id, label, target, stat_symbol_format=<factory>, p_format='p = {p:.3f}', alpha_thresholds=<factory>, effect_label_format=<factory>, n_format='n_{%s} = %d', decimal_places_p=3, decimal_places_stat=2, decimal_places_effect=2)

decimal_places_effect: int = 2

decimal_places_p: int = 3

decimal_places_stat: int = 2

format_effect(name, value)

Format an effect size.

Parameters:

• name (str) – Effect size name (e.g., “cohens_d_ind”).

• value (float) – Effect size value.

Returns:

Formatted effect size string.

Return type:

str

format_n(group, n)

Format a sample size.

Parameters:

• group (str) – Group name/label.

• n (int) – Sample size.

Returns:

Formatted sample size string.

Return type:

str

format_p(p_value)

Format a p-value.

Parameters:

p_value (float) – P-value to format.

Returns:

Formatted p-value string.

Return type:

str

format_stat(symbol, value, df=None)

Format a test statistic.

Parameters:

• symbol (str) – Statistic symbol (e.g., “t”, “F”, “chi2”).

• value (float) – Statistic value.

• df (float, optional) – Degrees of freedom.

Returns:

Formatted statistic string.

Return type:

str

n_format: str = 'n_{%s} = %d'

p_format: str = 'p = {p:.3f}'

p_to_stars(p_value)

Convert p-value to significance stars.

Parameters:

p_value (float) – P-value.

Returns:

Stars string (”*”, “”, “*”, or “ns”).

Return type:

str

id: str

label: str

target: Literal['latex', 'html', 'plain']

stat_symbol_format: Dict[str, str]

alpha_thresholds: List[Tuple[float, str]]

effect_label_format: Dict[str, str]

scitex_stats.recommend_tests(ctx, top_k=3, families=None)

Recommend tests for the given context.

Returns test names sorted by priority. Brunner-Munzel is the recommended default for 2-group comparisons (priority 110).

Parameters:

• ctx (StatContext) – Context inferred from figure/data.

• top_k (int) – Number of top tests to return.

• families (list of TestFamily or None) – Families to consider. If None, uses standard test families (parametric, nonparametric, categorical, correlation).

Returns:

test_names – Internal names of recommended tests, sorted by priority.

Return type:

list of str

Examples

>>> ctx = StatContext(
...     n_groups=2,
...     sample_sizes=[30, 32],
...     outcome_type="continuous",
...     design="between",
...     paired=False,
...     has_control_group=False,
...     n_factors=1
... )
>>> recommended = recommend_tests(ctx, top_k=3)
>>> "brunner_munzel" in recommended
True

scitex_stats.check_applicable(rule, ctx)

Check whether a given statistical test is applicable to the context.

This function evaluates all conditions in the TestRule against the StatContext and returns both the result and human-readable reasons for any failures (suitable for tooltips).

Parameters:

• rule (TestRule) – The rule definition for a specific test.

• ctx (StatContext) – The context inferred from the figure and data.

Return type:

Tuple[bool, List[str]]

Returns:

• ok (bool) – True if applicable, False otherwise.

• reasons (list of str) – If not applicable, human-readable reasons for tooltips.

Examples

>>> from scitex_stats.auto import StatContext, TEST_RULES, check_applicable
>>> ctx = StatContext(
...     n_groups=2,
...     sample_sizes=[30, 32],
...     outcome_type="continuous",
...     design="between",
...     paired=False,
...     has_control_group=False,
...     n_factors=1
... )
>>> rule = TEST_RULES["ttest_ind"]
>>> ok, reasons = check_applicable(rule, ctx)
>>> ok
True

>>> ctx.normality_ok = False
>>> ok, reasons = check_applicable(rule, ctx)
>>> ok
False
>>> "normality" in reasons[0].lower()
True

scitex_stats.get_stat_style(style_id)

Look up a statistical reporting style by its ID.

Parameters:

style_id (str) – Style identifier (e.g., “apa_latex”, “nature_html”).

Returns:

The requested style, or APA LaTeX as fallback.

Return type:

StatStyle

Examples

>>> style = get_stat_style("apa_latex")
>>> style.label
'APA (LaTeX)'

>>> style = get_stat_style("unknown")  # Falls back to APA
>>> style.id
'apa_latex'

scitex_stats.p_to_stars(p_value, style=None)

Convert p-value to significance stars.

Uses the alpha thresholds from the specified style.

Parameters:

• p_value (float or None) – P-value to convert.

• style (str or StatStyle, optional) – Style to use for thresholds.

Returns:

Stars string (”*”, “”, “*”, or “ns”).

Return type:

str

Examples

>>> p_to_stars(0.001)
'***'
>>> p_to_stars(0.03)
'*'
>>> p_to_stars(0.10)
'ns'

scitex_stats.test_ttest_ind(x, y, var_x='x', var_y='y', alternative='two-sided', equal_var=True, alpha=0.05, plot=False, ax=None, data=None, return_as='dict', verbose=False)

Perform independent samples t-test.

Parameters:

• x (array or Series) – First sample

• y (array or Series) – Second sample

• var_x (str, default 'x') – Label for first sample

• var_y (str, default 'y') – Label for second sample

• alternative ({'two-sided', 'greater', 'less'}, default 'two-sided') – Alternative hypothesis: - ‘two-sided’: means are different - ‘greater’: mean of x is greater than y - ‘less’: mean of x is less than y

• equal_var (bool, default True) – Assume equal population variances (Student’s t-test) If False, use Welch’s t-test

• alpha (float, default 0.05) – Significance level

• plot (bool, default False) – Whether to generate visualization

• ax (matplotlib.axes.Axes, optional) – Axes object to plot on. If None and plot=True, creates new figure. If provided, automatically enables plotting.

• data (DataFrame, str, or None, optional) – DataFrame or CSV path. When provided, string values for x/y are resolved as column names (seaborn-style).

• return_as ({'dict', 'dataframe'}, default 'dict') – Output format

• verbose (bool, default False) – Whether to print test results

Returns:

results – Test results including: - test_method: Name of test performed - statistic: t-statistic value - pvalue: p-value - stars: Significance stars - significant: Whether null hypothesis is rejected - effect_size: Cohen’s d - power: Statistical power - n_x, n_y: Sample sizes - var_x, var_y: Variable labels - H0: Null hypothesis description

Return type:

dict or DataFrame

Notes

The independent samples t-test compares means of two independent groups.

Null hypothesis: μ_x = μ_y Alternative (two-sided): μ_x ≠ μ_y

The t-statistic is computed as:

\[\begin{split}t = \\frac{\\bar{x} - \\bar{y}}{s_p \\sqrt{\\frac{1}{n_x} + \\frac{1}{n_y}}}\end{split}\]

where \(s_p\) is the pooled standard deviation.

For Welch’s t-test (unequal variances), the denominator uses separate variances and degrees of freedom are adjusted.

References

[1]

Student (1908). “The Probable Error of a Mean”. Biometrika, 6(1), 1-25.

[2]

Welch, B. L. (1947). “The generalization of ‘Student’s’ problem when several different population variances are involved”. Biometrika, 34(1-2), 28-35.

Examples

>>> x = np.array([1, 2, 3, 4, 5])
>>> y = np.array([2, 3, 4, 5, 6])
>>> result = test_ttest_ind(x, y)
>>> result['pvalue']
0.109...

>>> # With auto-created figure
>>> result = test_ttest_ind(x, y, plot=True)

>>> # Plot on existing axes
>>> fig, ax = plt.subplots()
>>> result = test_ttest_ind(x, y, ax=ax)

>>> # As DataFrame
>>> df = test_ttest_ind(x, y, return_as='dataframe')
>>> df['stars'].iloc[0]
'ns'

scitex_stats.test_ttest_rel(x, y, var_x='before', var_y='after', alternative='two-sided', alpha=0.05, plot=False, ax=None, data=None, return_as='dict')

Perform paired samples t-test (related/dependent samples).

Parameters:

• x (array or Series) – First sample (e.g., pre-test, baseline)

• y (array or Series) – Second sample (e.g., post-test, follow-up) Must have same length as x

• var_x (str, default 'before') – Label for first sample

• var_y (str, default 'after') – Label for second sample

• alternative ({'two-sided', 'greater', 'less'}, default 'two-sided') – Alternative hypothesis: - ‘two-sided’: means differ - ‘greater’: mean(x - y) > 0 - ‘less’: mean(x - y) < 0

• alpha (float, default 0.05) – Significance level

• plot (bool, default False) – Whether to generate visualization

• ax (matplotlib.axes.Axes, optional) – Axes object to plot on. If None and plot=True, creates new figure. If provided, automatically enables plotting.

• data (DataFrame, str, or None, optional) – DataFrame or CSV path. When provided, string values for x/y are resolved as column names (seaborn-style).

• return_as ({'dict', 'dataframe'}, default 'dict') – Output format

Returns:

results – Test results (same structure as test_ttest_ind)

Return type:

dict or DataFrame

Notes

The paired t-test compares means of matched observations (within-subjects).

When to use: - Before-after measurements on same subjects - Matched pairs (twins, siblings, matched controls) - Repeated measures at two time points

Assumptions: - Differences (x - y) are normally distributed - Pairs are independent across subjects - No assumption about equality of variances

The test statistic is:

\[\begin{split}t = \\frac{\\bar{d}}{s_d / \\sqrt{n}}\end{split}\]

where \(\\bar{d}\) is mean difference and \(s_d\) is SD of differences.

Effect size (Cohen’s d for paired samples):

\[\begin{split}d = \\frac{\\bar{d}}{s_d}\end{split}\]

This measures the standardized change from baseline.

References

[1]

Student (1908). “The Probable Error of a Mean”. Biometrika, 6(1), 1-25.

Examples

>>> before = np.array([10, 12, 15, 18, 20])
>>> after = np.array([12, 14, 17, 20, 22])
>>> result = test_ttest_rel(before, after)
>>> result['pvalue']
0.001...

>>> # With visualization
>>> fig, ax = plt.subplots()
>>> result = test_ttest_rel(before, after, ax=ax)
>>> plt.show()

scitex_stats.test_ttest_1samp(x, popmean=0, var_x='sample', alternative='two-sided', alpha=0.05, plot=False, ax=None, data=None, return_as='dict')

Perform one-sample t-test.

Parameters:

• x (array or Series) – Sample data

• popmean (float, default 0) – Expected population mean (null hypothesis value)

• var_x (str, default 'sample') – Label for sample

• alternative ({'two-sided', 'greater', 'less'}, default 'two-sided') – Alternative hypothesis: - ‘two-sided’: mean ≠ popmean - ‘greater’: mean > popmean - ‘less’: mean < popmean

• alpha (float, default 0.05) – Significance level

• ax (matplotlib.axes.Axes, optional) – Axes object to plot on. If provided, plots visualization on given axes.

• data (DataFrame, str, or None, optional) – DataFrame or CSV path. When provided, string value for x is resolved as a column name (seaborn-style).

• return_as ({'dict', 'dataframe'}, default 'dict') – Output format

Returns:

results – Test results

Return type:

dict or DataFrame

Notes

The one-sample t-test compares sample mean to a known population mean.

When to use: - Test if sample mean differs from theoretical/known value - Compare observed data to standard/reference value - Test if mean differs from zero (common in difference scores)

Assumptions: - Data are normally distributed - Observations are independent

The test statistic is:

\[\begin{split}t = \\frac{\\bar{x} - \\mu_0}{s / \\sqrt{n}}\end{split}\]

where \(\\mu_0\) is the hypothesized population mean.

Effect size (Cohen’s d for one sample):

\[\begin{split}d = \\frac{\\bar{x} - \\mu_0}{s}\end{split}\]

References

[1]

Student (1908). “The Probable Error of a Mean”. Biometrika, 6(1), 1-25.

Examples

>>> # Test if sample mean differs from 0
>>> x = np.array([1, 2, 3, 4, 5])
>>> result = test_ttest_1samp(x, popmean=0)
>>> result['pvalue']
0.003...

>>> # Test if sample mean differs from 100
>>> scores = np.array([95, 98, 102, 105, 108])
>>> result = test_ttest_1samp(scores, popmean=100)

scitex_stats.test_anova(groups=None, var_names=None, alpha=0.05, check_assumptions=True, plot=False, ax=None, data=None, value_col=None, group_col=None, return_as='dict', decimals=3, verbose=False)

Perform one-way ANOVA for independent samples.

Parameters:

• groups (list of arrays) – List of sample arrays for each group (minimum 2 groups)

• var_names (list of str, optional) – Names for each group. If None, uses ‘Group 1’, ‘Group 2’, etc.

• alpha (float, default 0.05) – Significance level

• check_assumptions (bool, default True) – Whether to check normality and homogeneity assumptions

• plot (bool, default False) – Whether to generate visualization

• ax (matplotlib.axes.Axes, optional) – Axes object to plot on. If None and plot=True, creates new figure. If provided, automatically enables plotting.

• data (DataFrame, str, or None, optional) – DataFrame or CSV path. When provided with value_col and group_col, groups are extracted automatically (seaborn-style).

• value_col (str, optional) – Column containing measurement values (used with data=).

• group_col (str, optional) – Column containing group labels (used with data=).

• return_as ({'dict', 'dataframe'}, default 'dict') – Output format

• decimals (int, default 3) – Number of decimal places for rounding

• verbose (bool, default False) – Whether to print test results

Returns:

results – Test results including: - test_method: ‘One-way ANOVA’ - statistic: F-statistic value - pvalue: p-value - stars: Significance stars - significant: Whether null hypothesis is rejected - effect_size: Eta-squared (η²) - effect_size_metric: ‘eta-squared’ - effect_size_interpretation: Interpretation of eta-squared - n_groups: Number of groups - n_samples: Sample sizes for each group - df_between: Degrees of freedom between groups - df_within: Degrees of freedom within groups - var_names: Group labels - assumptions_met: Whether assumptions are satisfied - H0: Null hypothesis description

Return type:

dict or DataFrame

Notes

One-way ANOVA (Analysis of Variance) tests whether samples from different groups have the same population mean.

Null Hypothesis (H0): All groups have equal population means

Alternative Hypothesis (H1): At least one group mean differs

Assumptions: 1. Independence: Observations within and between groups are independent 2. Normality: Data in each group are normally distributed

• Can be checked with test_shapiro()

• Robust to moderate violations with large samples (n > 30 per group)

3. Homogeneity of variance: Groups have equal population variances - Can be checked with Levene’s test - If violated, consider Welch’s ANOVA or non-parametric alternative

When assumptions are violated: - Non-normality: Use test_kruskal() (Kruskal-Wallis test) - Unequal variances: Use Welch’s ANOVA (not yet implemented) - Outliers present: Use test_kruskal() or remove outliers

F-Statistic:

\[\begin{split}F = \\frac{MS_{between}}{MS_{within}} = \\frac{SS_{between}/(k-1)}{SS_{within}/(N-k)}\end{split}\]

Where: - k: Number of groups - N: Total sample size - SS: Sum of squares - MS: Mean square

Effect Size (Eta-squared):

\[\begin{split}\\eta^2 = \\frac{SS_{between}}{SS_{total}}\end{split}\]

Interpretation: - η² < 0.01: negligible - η² < 0.06: small - η² < 0.14: medium - η² ≥ 0.14: large

Post-hoc tests: If significant, perform pairwise comparisons with correction: - test_ttest_ind() for all pairs (if assumptions met) - test_brunner_munzel() for all pairs (robust alternative) - correct_bonferroni() or correct_fdr() for multiple comparisons

References

[1]

Fisher, R. A. (1925). Statistical Methods for Research Workers. Oliver and Boyd.

[2]

Cohen, J. (1988). Statistical Power Analysis for the Behavioral Sciences (2nd ed.). Routledge.

[3]

Maxwell, S. E., & Delaney, H. D. (2004). Designing Experiments and Analyzing Data: A Model Comparison Perspective (2nd ed.). Psychology Press.

Examples

>>> # Three groups with different means
>>> group1 = np.array([1, 2, 3, 4, 5])
>>> group2 = np.array([3, 4, 5, 6, 7])
>>> group3 = np.array([5, 6, 7, 8, 9])
>>> result = test_anova([group1, group2, group3])
>>> result['rejected']
True

>>> # With auto-created figure
>>> result = test_anova(
...     [group1, group2, group3],
...     var_names=['Control', 'Treatment 1', 'Treatment 2'],
...     plot=True
... )

>>> # Plot on existing axes
>>> fig, ax = plt.subplots()
>>> result = test_anova([group1, group2, group3], ax=ax)

>>> # Export results
>>> from scitex_stats.utils._normalizers import convert_results
>>> convert_results(result, return_as='excel', path='anova_results.xlsx')

scitex_stats.test_anova_rm(data, subject_col=None, condition_col=None, value_col=None, condition_names=None, alpha=0.05, correction='auto', check_sphericity=True, plot=False, ax=None, return_as='dict', decimals=3, verbose=False)

Perform repeated measures ANOVA for within-subjects designs.

Parameters:

• data (array or DataFrame) –

  • If array: shape (n_subjects, n_conditions), wide format

  • If DataFrame with subject_col/condition_col: long format

  • If DataFrame without: wide format (rows=subjects, cols=conditions)

• subject_col (str, optional) – Column name for subject IDs (long format)

• condition_col (str, optional) – Column name for conditions (long format)

• value_col (str, optional) – Column name for values (long format)

• condition_names (list of str, optional) – Names for conditions (wide format)

• alpha (float, default 0.05) – Significance level

• correction ({'auto', 'none', 'gg'}, default 'auto') – Correction method: - ‘auto’: Apply GG correction if sphericity violated - ‘none’: No correction - ‘gg’: Always apply Greenhouse-Geisser correction

• check_sphericity (bool, default True) – Whether to test sphericity assumption

• plot (bool, default False) – Whether to generate profile plot

• ax (matplotlib.axes.Axes, optional) – Axes object to plot on. If None and plot=True, creates new figure. If provided, automatically enables plotting.

• return_as ({'dict', 'dataframe'}, default 'dict') – Output format

• decimals (int, default 3) – Number of decimal places for rounding

• verbose (bool, default False) – Whether to print test results

Return type:

Union[dict, DataFrame, Tuple]

Returns:

• result (dict or DataFrame) – Test results including: - statistic: F-statistic - pvalue: p-value (possibly corrected) - df_effect: Degrees of freedom for effect - df_error: Degrees of freedom for error - effect_size: Partial eta-squared - sphericity_W: Mauchly’s W (if checked) - sphericity_pvalue: Sphericity test p-value - sphericity_met: Whether sphericity assumption met - epsilon_gg: Greenhouse-Geisser epsilon - correction_applied: Which correction was applied - significant: Whether to reject null hypothesis

• If plot=True, returns tuple of (result, figure)

Notes

Repeated measures ANOVA tests whether the means differ across multiple conditions measured on the same subjects (within-subjects factor).

Null Hypothesis (H0): All condition means are equal

Assumptions: 1. Independence of subjects: Different subjects are independent 2. Normality: Differences between conditions are normally distributed 3. Sphericity: Variances of differences between all pairs of conditions

are equal (tested with Mauchly’s test)

Sphericity: The sphericity assumption is unique to repeated measures ANOVA. If violated: - Greenhouse-Geisser correction: More conservative, use when ε < 0.75 - Huynh-Feldt correction: Less conservative (not implemented) - Multivariate approach: MANOVA (not implemented)

Greenhouse-Geisser Correction: Adjusts degrees of freedom by multiplying by epsilon (ε): - df_effect_adj = ε × df_effect - df_error_adj = ε × df_error

Effect Size (Partial η²):

\[\begin{split}\\eta_p^2 = \\frac{SS_{effect}}{SS_{effect} + SS_{error}}\end{split}\]

Interpretation same as regular eta-squared: - < 0.01: negligible - < 0.06: small - < 0.14: medium - ≥ 0.14: large

Post-hoc tests: If significant, use pairwise t-tests with correction: - test_ttest_rel() for all pairs - correct_bonferroni() or correct_holm() for multiple comparisons

Examples

>>> import numpy as np
>>> from scitex_stats.tests.parametric import test_anova_rm
>>>
>>> # Wide format: subjects × conditions
>>> data = np.array([
...     [5.2, 6.1, 7.3, 6.8],  # Subject 1
...     [4.8, 5.9, 6.7, 6.2],  # Subject 2
...     [5.5, 6.4, 7.1, 7.0],  # Subject 3
...     [4.9, 5.7, 6.9, 6.5],  # Subject 4
... ])
>>>
>>> result = test_anova_rm(
...     data,
...     condition_names=['Baseline', 'Week 1', 'Week 2', 'Week 3'],
...     plot=True
... )
>>>
>>> print(f"F = {result['statistic']:.2f}, p = {result['pvalue']:.4f}")
>>> print(f"Sphericity met: {result['sphericity_met']}")
>>> print(f"Partial η² = {result['effect_size']:.3f}")

References

[1]

Greenhouse, S. W., & Geisser, S. (1959). “On methods in the analysis of profile data”. Psychometrika, 24(2), 95-112.

[2]

Mauchly, J. W. (1940). “Significance test for sphericity of a normal n-variate distribution”. The Annals of Mathematical Statistics, 11(2), 204-209.

See also

test_anova

One-way ANOVA for independent samples

test_friedman

Non-parametric alternative (no sphericity assumption)

scitex_stats.test_anova_2way(data, factor_a=None, factor_b=None, value=None, factor_a_name='Factor A', factor_b_name='Factor B', alpha=0.05, check_assumptions=True, plot=False, ax=None, return_as='dict', decimals=3, verbose=False)

Perform two-way ANOVA for factorial designs.

Parameters:

• data (DataFrame or array) –

  • If DataFrame: requires factor_a, factor_b, value column names

  • If array: 2D or 3D array (see factor_a, factor_b parameters)

• factor_a (str or array, optional) –

  • If str: column name for factor A in DataFrame

  • If array: factor A levels for each observation

• factor_b (str or array, optional) –

  • If str: column name for factor B in DataFrame

  • If array: factor B levels for each observation

• value (str, optional) – Column name for dependent variable (required if data is DataFrame)

• factor_a_name (str, default 'Factor A') – Name for factor A

• factor_b_name (str, default 'Factor B') – Name for factor B

• alpha (float, default 0.05) – Significance level

• check_assumptions (bool, default True) – Whether to check normality and homogeneity assumptions

• plot (bool, default False) – Whether to generate interaction plot

• ax (matplotlib.axes.Axes, optional) – Axes object to plot on. If None and plot=True, creates new figure. If provided, automatically enables plotting.

• return_as ({'dict', 'dataframe'}, default 'dict') – Output format

• decimals (int, default 3) – Number of decimal places for rounding

• verbose (bool, default False) – Whether to print test results

Return type:

Union[dict, DataFrame, Tuple]

Returns:

• result (dict or DataFrame) – Test results including for each effect (A, B, interaction): - effect: Name of effect - statistic: F-statistic - pvalue: p-value - df_effect: Degrees of freedom for effect - df_error: Degrees of freedom for error - effect_size: Partial eta-squared - rejected: Whether to reject null hypothesis - significant: Same as rejected

• If plot=True, returns tuple of (result, figure)

Notes

Two-way ANOVA tests the effects of two independent categorical variables (factors) on a continuous dependent variable, including their interaction.

Three Hypotheses Tested: 1. Main effect of Factor A: Marginal means of A levels differ 2. Main effect of Factor B: Marginal means of B levels differ 3. Interaction A×B: Effect of A depends on level of B (and vice versa)

Null Hypotheses: - H0_A: All marginal means of Factor A are equal - H0_B: All marginal means of Factor B are equal - H0_AB: No interaction between Factors A and B

Assumptions: 1. Independence: Observations are independent 2. Normality: Residuals are normally distributed within each cell 3. Homogeneity of variance: Equal variances across all cells

Sum of Squares Decomposition:

\[SS_{total} = SS_A + SS_B + SS_{AB} + SS_{error}\]

Where: - SS_A: Sum of squares for main effect A - SS_B: Sum of squares for main effect B - SS_AB: Sum of squares for interaction A×B - SS_error: Sum of squares for error (within cells)

F-statistics:

\[\begin{split}F_A = \\frac{MS_A}{MS_{error}}, \\quad F_B = \\frac{MS_B}{MS_{error}}, \\quad F_{AB} = \\frac{MS_{AB}}{MS_{error}}\end{split}\]

Effect Size (Partial η²):

\[\begin{split}\\eta_p^2 = \\frac{SS_{effect}}{SS_{effect} + SS_{error}}\end{split}\]

Interpreting Results: - Significant interaction: Main effects should be interpreted cautiously.

Use simple effects analysis or interaction plots.

• Non-significant interaction: Main effects can be interpreted directly.

Post-hoc tests: If main effects are significant: - Pairwise comparisons with test_ttest_ind() - Apply corrections: correct_bonferroni(), correct_holm()

If interaction is significant: - Simple effects: test effect of A at each level of B - Pairwise comparisons within each level

Examples

>>> import pandas as pd
>>> import numpy as np
>>> from scitex_stats.tests.parametric import test_anova_2way
>>>
>>> # Example: Drug (2 levels) × Gender (2 levels)
>>> np.random.seed(42)
>>> n_per_cell = 10
>>>
>>> data = pd.DataFrame({
...     'Drug': ['Placebo']*20 + ['Active']*20,
...     'Gender': (['Male']*10 + ['Female']*10) * 2,
...     'Score': np.concatenate([
...         np.random.normal(50, 10, 10),  # Placebo, Male
...         np.random.normal(55, 10, 10),  # Placebo, Female
...         np.random.normal(65, 10, 10),  # Active, Male
...         np.random.normal(75, 10, 10),  # Active, Female (interaction)
...     ])
... })
>>>
>>> result = test_anova_2way(
...     data,
...     factor_a='Drug',
...     factor_b='Gender',
...     value='Score',
...     plot=True
... )
>>>
>>> for effect in result:
...     print(f"{effect['effect']}: F = {effect['statistic']:.2f}, p = {effect['pvalue']:.4f}")

References

[1]

Fisher, R. A. (1925). Statistical Methods for Research Workers.

[2]

Montgomery, D. C. (2017). Design and Analysis of Experiments (9th ed.).

See also

test_anova

One-way ANOVA

test_anova_rm

Repeated measures ANOVA

scitex_stats.test_brunner_munzel(x, y, var_x='x', var_y='y', alternative='two-sided', alpha=0.05, plot=False, ax=None, data=None, return_as='dict', verbose=False)

Perform Brunner-Munzel test (non-parametric).

Parameters:

• x (array or Series) – First sample

• y (array or Series) – Second sample

• var_x (str, default 'x') – Label for first sample

• var_y (str, default 'y') – Label for second sample

• alternative ({'two-sided', 'greater', 'less'}, default 'two-sided') – Alternative hypothesis: - ‘two-sided’: distributions differ - ‘greater’: x tends to be greater than y - ‘less’: x tends to be less than y

• alpha (float, default 0.05) – Significance level

• plot (bool, default False) – Whether to generate visualization

• ax (matplotlib.axes.Axes, optional) – Axes object to plot on. If None and plot=True, creates new figure. If provided, automatically enables plotting.

• data (DataFrame, str, or None, optional) – DataFrame or CSV path. When provided, string values for x/y are resolved as column names (seaborn-style).

• return_as ({'dict', 'dataframe'}, default 'dict') – Output format

• verbose (bool, default False) – Whether to print test results

Returns:

results – Test results including: - test_method: ‘Brunner-Munzel test’ - statistic_name: ‘W’ - statistic: W-statistic value - pvalue: p-value - stars: Significance stars - rejected: Whether null hypothesis is rejected - effect_size: P(X > Y) (primary effect size) - effect_size_metric: ‘P(X>Y)’ - effect_size_interpretation: Interpretation of P(X>Y) - effect_size_secondary: Cliff’s delta (secondary effect size) - effect_size_secondary_metric: “Cliff’s delta” - effect_size_secondary_interpretation: Interpretation of delta - n_x, n_y: Sample sizes - var_x, var_y: Variable labels - H0: Null hypothesis description

Return type:

dict or DataFrame

Notes

The Brunner-Munzel test is a non-parametric test for comparing two independent samples. It is more robust than the t-test when: - Distributions are non-normal - Variances are unequal - Sample sizes differ - Data contain outliers

Unlike Mann-Whitney U test, Brunner-Munzel does not assume equal variances and provides better control of Type I error rate.

The test statistic W is approximately t-distributed:

\[W = \frac{\hat{p} - 0.5}{\sqrt{\hat{\sigma}^2}}\]

where \(\hat{p}\) is an estimate of P(X > Y).

Effect Sizes:

1. P(X > Y): Probability that a random value from X exceeds a random value from Y. Interpretation: - 0.50: No effect (chance) - 0.56: Small effect - 0.64: Medium effect - 0.71: Large effect

2. Cliff’s delta (δ): Ranges from -1 to 1, related to P(X>Y) by: δ = 2×P(X>Y) - 1. Interpretation: - |δ| < 0.147: Negligible - |δ| < 0.33: Small - |δ| < 0.474: Medium - |δ| ≥ 0.474: Large

References

[1]

Brunner, E., & Munzel, U. (2000). “The nonparametric Behrens-Fisher problem: Asymptotic theory and a small-sample approximation”. Biometrical Journal, 42(1), 17-25.

[2]

Neubert, K., & Brunner, E. (2007). “A studentized permutation test for the non-parametric Behrens-Fisher problem”. Computational Statistics & Data Analysis, 51(10), 5192-5204.

Examples

>>> x = np.array([1, 2, 3, 4, 5])
>>> y = np.array([2, 3, 4, 5, 6])
>>> result = test_brunner_munzel(x, y)
>>> result['pvalue']
0.109...
>>> result['effect_size']  # P(X > Y)
0.2
>>> result['effect_size_secondary']  # Cliff's delta
-0.6

>>> # With auto-created figure
>>> result = test_brunner_munzel(x, y, plot=True)

>>> # Plot on existing axes
>>> fig, ax = plt.subplots()
>>> result = test_brunner_munzel(x, y, ax=ax)

>>> # As DataFrame
>>> df = test_brunner_munzel(x, y, return_as='dataframe')

scitex_stats.test_wilcoxon(x, y, var_x='before', var_y='after', alternative='two-sided', alpha=0.05, plot=False, ax=None, data=None, return_as='dict', verbose=False)

Perform Wilcoxon signed-rank test (non-parametric paired test).

Parameters:

• x (array or Series) – First sample (e.g., pre-test, baseline)

• y (array or Series) – Second sample (e.g., post-test, follow-up) Must have same length as x

• var_x (str, default 'before') – Label for first sample

• var_y (str, default 'after') – Label for second sample

• alternative ({'two-sided', 'greater', 'less'}, default 'two-sided') – Alternative hypothesis: - ‘two-sided’: distributions differ - ‘greater’: x tends to be greater than y - ‘less’: x tends to be less than y

• alpha (float, default 0.05) – Significance level

• plot (bool, default False) – Whether to generate visualization

• ax (matplotlib.axes.Axes, optional) – Axes object to plot on. If None and plot=True, creates new figure. If provided, automatically enables plotting.

• data (DataFrame, str, or None, optional) – DataFrame or CSV path. When provided, string values for x/y are resolved as column names (seaborn-style).

• return_as ({'dict', 'dataframe'}, default 'dict') – Output format

• verbose (bool, default False) – Whether to print test results

Returns:

results – Test results including: - test_method: ‘Wilcoxon signed-rank test’ - statistic: W-statistic (sum of signed ranks) - pvalue: p-value - stars: Significance stars - significant: Whether null hypothesis is rejected - effect_size: rank-biserial correlation - effect_size_metric: ‘rank-biserial correlation’ - n_pairs: number of pairs (excluding zeros) - n_zeros: number of zero differences (ties)

Return type:

dict or DataFrame

Notes

The Wilcoxon signed-rank test is the non-parametric alternative to the paired t-test. It tests whether the median of differences is zero.

When to use: - Paired samples (before-after, matched pairs) - Data are not normally distributed - Ordinal data or continuous data with outliers - Robust alternative to paired t-test

Assumptions: - Paired observations - Differences are symmetric around the median - Ordinal or continuous data

How it works: 1. Compute differences: d = x - y 2. Remove zero differences 3. Rank absolute differences 4. Sum ranks of positive differences (W+) 5. Sum ranks of negative differences (W-) 6. Test statistic: W = min(W+, W-)

Effect size (rank-biserial correlation):

\[r = \frac{W_+ - W_-}{n(n+1)/2}\]

Ranges from -1 to 1: - r close to 1: x > y (large positive effect) - r close to 0: no difference - r close to -1: x < y (large negative effect)

Interpretation: - |r| < 0.1: negligible - |r| < 0.3: small - |r| < 0.5: medium - |r| ≥ 0.5: large

References

[1]

Wilcoxon, F. (1945). “Individual comparisons by ranking methods”. Biometrics Bulletin, 1(6), 80-83.

[2]

Kerby, D. S. (2014). “The simple difference formula: An approach to teaching nonparametric correlation”. Comprehensive Psychology, 3, 11.

Examples

>>> before = np.array([10, 12, 15, 18, 20])
>>> after = np.array([12, 14, 17, 20, 22])
>>> result = test_wilcoxon(before, after)
>>> result['pvalue']
0.062...

>>> # With visualization
>>> result, fig = test_wilcoxon(before, after, plot=True)

scitex_stats.test_kruskal(groups=None, var_names=None, alpha=0.05, plot=False, ax=None, data=None, value_col=None, group_col=None, return_as='dict', decimals=3, verbose=False)

Perform Kruskal-Wallis H test for independent samples.

Parameters:

• groups (list of arrays) – List of sample arrays for each group (minimum 2 groups)

• var_names (list of str, optional) – Names for each group. If None, uses ‘Group 1’, ‘Group 2’, etc.

• alpha (float, default 0.05) – Significance level

• plot (bool, default False) – Whether to generate box plots

• ax (matplotlib.axes.Axes, optional) – Axes object to plot on. If None and plot=True, creates new figure. If provided, automatically enables plotting.

• data (DataFrame, str, or None, optional) – DataFrame or CSV path. When provided with value_col and group_col, groups are extracted automatically (seaborn-style).

• value_col (str, optional) – Column containing measurement values (used with data=).

• group_col (str, optional) – Column containing group labels (used with data=).

• return_as ({'dict', 'dataframe'}, default 'dict') – Output format

• decimals (int, default 3) – Number of decimal places for rounding

• verbose (bool, default False) – Whether to print test results

Returns:

results – Test results including: - test_method: ‘Kruskal-Wallis H test’ - statistic: H-statistic value - pvalue: p-value - stars: Significance stars - significant: Whether null hypothesis is rejected - effect_size: Epsilon-squared (ε²) - effect_size_metric: ‘epsilon-squared’ - effect_size_interpretation: Interpretation of epsilon-squared - n_groups: Number of groups - n_samples: Sample sizes for each group - var_names: Group labels - H0: Null hypothesis description

Return type:

dict or DataFrame

Notes

The Kruskal-Wallis H test is a non-parametric alternative to one-way ANOVA. It tests whether samples originate from the same distribution by comparing the ranks of observations across groups.

Null Hypothesis (H0): All groups have the same population median (more precisely: all groups have identical distribution functions)

Assumptions: - Independent observations within and between groups - Ordinal or continuous data - Similar distribution shapes across groups (for median interpretation)

Advantages over ANOVA: - No normality assumption required - Robust to outliers - Works with ordinal data - More powerful than ANOVA for heavy-tailed distributions

When to use: - Comparing 3+ independent groups - Data violate normality (use test_shapiro to check) - Presence of outliers - Ordinal data (e.g., Likert scales)

Test Statistic H:

\[H = \frac{12}{N(N+1)} \sum_{i=1}^{k} \frac{R_i^2}{n_i} - 3(N+1)\]

Where: - k: Number of groups - N: Total sample size - R_i: Sum of ranks for group i - n_i: Sample size of group i

Effect Size (Epsilon-squared):

\[\epsilon^2 = \frac{H - k + 1}{N - k}\]

Interpretation (similar to eta-squared): - ε² < 0.01: negligible - ε² < 0.06: small - ε² < 0.14: medium - ε² ≥ 0.14: large

Post-hoc tests: If significant, use pairwise comparisons with correction: - test_brunner_munzel() for all pairs - correct_bonferroni() or correct_fdr() for multiple comparisons

Tied ranks: Handled automatically by scipy.stats.kruskal()

References

[1]

Kruskal, W. H., & Wallis, W. A. (1952). “Use of ranks in one-criterion variance analysis”. Journal of the American Statistical Association, 47(260), 583-621.

[2]

Hecke, T. V. (2012). “Power study of ANOVA versus Kruskal-Wallis test”. Journal of Statistics and Management Systems, 15(2-3), 241-247.

[3]

Tomczak, M., & Tomczak, E. (2014). “The need to report effect size estimates revisited”. Trends in Sport Sciences, 21(1), 19-25.

Examples

>>> # Three groups with different medians
>>> group1 = np.array([1, 2, 3, 4, 5])
>>> group2 = np.array([3, 4, 5, 6, 7])
>>> group3 = np.array([5, 6, 7, 8, 9])
>>> result = test_kruskal([group1, group2, group3])
>>> result['rejected']
True

>>> # With custom names and plot
>>> result, fig = test_kruskal(
...     [group1, group2, group3],
...     var_names=['Control', 'Treatment 1', 'Treatment 2'],
...     plot=True
... )

>>> # Export results
>>> from scitex_stats.utils._normalizers import convert_results
>>> convert_results(result, return_as='excel', path='kruskal_results.xlsx')

scitex_stats.test_mannwhitneyu(x, y, var_x='x', var_y='y', alternative='two-sided', alpha=0.05, plot=False, ax=None, data=None, return_as='dict', decimals=3, verbose=False)

Perform Mann-Whitney U test (Wilcoxon rank-sum test).

Parameters:

• x (arrays or Series) – Two independent samples to compare

• y (arrays or Series) – Two independent samples to compare

• var_x (str) – Labels for samples

• var_y (str) – Labels for samples

• alternative ({'two-sided', 'less', 'greater'}, default 'two-sided') – Alternative hypothesis

• alpha (float, default 0.05) – Significance level

• plot (bool, default False) – Whether to generate visualization

• ax (matplotlib.axes.Axes, optional) – Axes object to plot on. If None and plot=True, creates new figure. If provided, automatically enables plotting.

• data (DataFrame, str, or None, optional) – DataFrame or CSV path. When provided, string values for x/y are resolved as column names (seaborn-style).

• return_as ({'dict', 'dataframe'}, default 'dict') – Output format

• decimals (int, default 3) – Number of decimal places for rounding

• verbose (bool, default False) – Whether to print test results

Returns:

results – Test results including: - test_method: ‘Mann-Whitney U test’ - statistic: U-statistic value - pvalue: p-value - stars: Significance stars - significant: Whether null hypothesis is rejected - effect_size: Rank-biserial correlation - effect_size_metric: ‘rank-biserial correlation’ - effect_size_interpretation: Interpretation - n_x, n_y: Sample sizes - var_x, var_y: Variable labels - H0: Null hypothesis description

Return type:

dict or DataFrame

Notes

The Mann-Whitney U test (also known as Wilcoxon rank-sum test) is a non-parametric test for comparing two independent samples.

Null Hypothesis (H0): The two samples come from distributions with equal medians (more precisely: P(X > Y) = 0.5)

Test Statistic U:

\[U = n_1 n_2 + \frac{n_1(n_1+1)}{2} - R_1\]

Where: - n_1, n_2: Sample sizes - R_1: Sum of ranks for sample 1

Effect Size (Rank-biserial correlation):

\[r = 1 - \frac{2U}{n_1 n_2}\]

Or equivalently:

\[r = \frac{2(\bar{R}_1 - \bar{R}_2)}{n_1 + n_2}\]

Interpretation: - |r| < 0.1: negligible - |r| < 0.3: small - |r| < 0.5: medium - |r| ≥ 0.5: large

Advantages: - No normality assumption required - Robust to outliers - Works with ordinal data - More powerful than t-test for non-normal data

When to use: - Comparing two independent groups - Data violate normality - Presence of outliers - Ordinal data (e.g., Likert scales) - Small sample sizes

Comparison with other tests: - vs t-test: More robust, less powerful when assumptions met - vs Brunner-Munzel: MWU assumes identical shape, BM does not - vs KS test: MWU tests location, KS tests entire distribution

Note on relationship to Brunner-Munzel: Mann-Whitney U assumes samples have the same distribution shape (differing only in location). For more robust analysis without this assumption, use test_brunner_munzel() instead.

References

[1]

Mann, H. B., & Whitney, D. R. (1947). “On a test of whether one of two random variables is stochastically larger than the other”. Annals of Mathematical Statistics, 18(1), 50-60.

[2]

Kerby, D. S. (2014). “The simple difference formula: An approach to teaching nonparametric correlation”. Comprehensive Psychology, 3, 11.

Examples

>>> # Basic usage
>>> x = np.array([1, 2, 3, 4, 5])
>>> y = np.array([3, 4, 5, 6, 7])
>>> result = test_mannwhitneyu(x, y)
>>> result['rejected']
True

>>> # With auto-created figure
>>> result = test_mannwhitneyu(x, y, plot=True)

>>> # Plot on existing axes
>>> fig, ax = plt.subplots()
>>> result = test_mannwhitneyu(x, y, ax=ax)

>>> # With verbose output
>>> result = test_mannwhitneyu(x, y, verbose=True)

scitex_stats.test_friedman(data, subject_col=None, condition_col=None, value_col=None, condition_names=None, alpha=0.05, plot=False, ax=None, return_as='dict', decimals=3, verbose=False)

Perform Friedman test for repeated measures (non-parametric).

Non-parametric alternative to repeated measures ANOVA. Tests whether distributions differ across 3+ related samples using ranks.

Parameters:

• data (array or DataFrame) –

  • If array: shape (n_subjects, n_conditions), wide format

  • If DataFrame with subject_col/condition_col: long format

  • If DataFrame without: wide format (rows=subjects, cols=conditions)

• subject_col (str, optional) – Column name for subject IDs (long format)

• condition_col (str, optional) – Column name for conditions (long format)

• value_col (str, optional) – Column name for values (long format)

• condition_names (list of str, optional) – Names for conditions (wide format)

• alpha (float, default 0.05) – Significance level

• plot (bool, default False) – Whether to generate visualization

• ax (matplotlib.axes.Axes, optional) – Axes object to plot on. If None and plot=True, creates new figure. If provided, automatically enables plotting.

• return_as ({'dict', 'dataframe'}, default 'dict') – Output format

• decimals (int, default 3) – Number of decimal places for rounding

• verbose (bool, default False) – Whether to print test results

Returns:

result – Test results including: - statistic: Chi-square statistic (Friedman’s χ²) - pvalue: p-value - df: Degrees of freedom (k - 1) - kendall_w: Kendall’s W (coefficient of concordance) - effect_size: Kendall’s W - effect_size_interpretation: interpretation - n_subjects: Number of subjects - n_conditions: Number of conditions - mean_ranks: Mean rank for each condition - significant: Whether to reject null hypothesis

Return type:

dict or DataFrame

Notes

The Friedman test is the non-parametric alternative to repeated measures ANOVA. It is used when: - Normality assumption is violated - Data are ordinal (e.g., Likert scales) - Sample sizes are small

Null Hypothesis (H0): All conditions have the same distribution

Alternative Hypothesis (H1): At least one condition differs

Procedure: 1. Rank observations within each subject (across conditions) 2. Compute sum of ranks for each condition 3. Calculate test statistic based on rank sums

Test Statistic:

\[\chi^2_F = \frac{12}{nk(k+1)} \sum_{j=1}^{k} R_j^2 - 3n(k+1)\]

Where: - n: Number of subjects - k: Number of conditions - R_j: Sum of ranks for condition j

Effect Size (Kendall’s W):

\[W = \frac{12 \sum_{j=1}^{k}(R_j - \bar{R})^2}{n^2(k^3 - k)}\]

Interpretation: - W < 0.1: negligible agreement - W < 0.3: weak agreement - W < 0.5: moderate agreement - W < 0.7: strong agreement - W ≥ 0.7: very strong agreement

Assumptions: - Paired/repeated observations (same subjects) - At least ordinal scale data - 3+ conditions (for 2 conditions, use Wilcoxon signed-rank test)

Post-hoc tests: If significant: - Pairwise Wilcoxon signed-rank tests - Apply corrections: correct_bonferroni(), correct_holm()

Advantages: - No normality assumption - Robust to outliers - Works with ordinal data - No sphericity assumption

Disadvantages: - Less powerful than RM-ANOVA when assumptions are met - Requires at least ordinal data - Sensitive to ties

Examples

>>> import numpy as np
>>> from scitex_stats.tests.nonparametric import test_friedman
>>>
>>> # Example: Pain ratings (ordinal) across 4 time points
>>> data = np.array([
...     [7, 6, 5, 4],  # Subject 1
...     [8, 7, 6, 5],  # Subject 2
...     [6, 5, 4, 3],  # Subject 3
...     [9, 8, 7, 6],  # Subject 4
... ])
>>>
>>> result = test_friedman(
...     data,
...     condition_names=['Baseline', '1 week', '2 weeks', '3 weeks'],
...     plot=True
... )
>>>
>>> print(f"χ² = {result['statistic']:.2f}, p = {result['pvalue']:.4f}")
>>> print(f"Kendall's W = {result['kendall_w']:.3f}")

References

[1]

Friedman, M. (1937). “The use of ranks to avoid the assumption of normality implicit in the analysis of variance”. Journal of the American Statistical Association, 32(200), 675-701.

[2]

Kendall, M. G., & Babington Smith, B. (1939). “The problem of m rankings”. The Annals of Mathematical Statistics, 10(3), 275-287.

See also

test_anova_rm

Parametric alternative (repeated measures ANOVA)

test_wilcoxon

For 2 related samples

test_kruskal

For 3+ independent samples

scitex_stats.test_pearson(x, y, var_x='x', var_y='y', alternative='two-sided', alpha=0.05, plot=False, ax=None, data=None, return_as='dict', decimals=3, verbose=False)

Perform Pearson correlation test.

Parameters:

• x (arrays or Series) – Two continuous variables

• y (arrays or Series) – Two continuous variables

• var_x (str) – Labels for variables

• var_y (str) – Labels for variables

• alternative ({'two-sided', 'less', 'greater'}, default 'two-sided') – Alternative hypothesis

• alpha (float, default 0.05) – Significance level for confidence interval

• plot (bool, default False) – Whether to generate scatter plot

• ax (matplotlib.axes.Axes, optional) – Axes object to plot on. If None and plot=True, creates new figure. If provided, automatically enables plotting.

• data (DataFrame, str, or None, optional) – DataFrame or CSV path. When provided, string values for x/y are resolved as column names (seaborn-style).

• return_as ({'dict', 'dataframe'}, default 'dict') – Output format

• decimals (int, default 3) – Number of decimal places for rounding

• verbose (bool, default False) – Whether to print test results

Returns:

results – Test results including: - test_method: ‘Pearson correlation’ - statistic: Pearson correlation coefficient - pvalue: p-value - stars: Significance stars - significant: Whether null hypothesis is rejected - ci_lower, ci_upper: Confidence interval bounds - r_squared: Coefficient of determination - effect_size: Correlation coefficient (same as statistic) - effect_size_metric: ‘Pearson r’ - effect_size_interpretation: Interpretation - n: Sample size (after removing NaN pairs) - var_x, var_y: Variable labels - H0: Null hypothesis description

Return type:

dict or DataFrame

Notes

Pearson correlation coefficient measures the linear relationship between two continuous variables.

Null Hypothesis (H0): No linear correlation (ρ = 0)

Pearson’s r:

\[\begin{split}r = \frac{\\sum(x_i - \bar{x})(y_i - \bar{y})}{\\sqrt{\\sum(x_i - \bar{x})^2 \\sum(y_i - \bar{y})^2}}\end{split}\]

Range: -1 ≤ r ≤ 1 - r = 1: Perfect positive linear relationship - r = 0: No linear relationship - r = -1: Perfect negative linear relationship

Coefficient of determination (R²):

\[R^2 = r^2\]

R² represents the proportion of variance in y explained by x.

Interpretation (Cohen, 1988): - |r| < 0.1: negligible - |r| < 0.3: small - |r| < 0.5: medium - |r| ≥ 0.5: large

Assumptions: 1. Linearity: Relationship between variables is linear 2. Normality: Both variables are normally distributed (for hypothesis testing) 3. Homoscedasticity: Variance is constant across the range 4. Independence: Observations are independent

When to use: - Assessing linear relationship between two continuous variables - Both variables approximately normally distributed - No major outliers present - Relationship appears linear on scatter plot

When NOT to use: - Non-linear relationships (consider transformation or Spearman) - Ordinal data (use Spearman) - Severe outliers present (use Spearman) - Non-normal distributions (use Spearman)

Confidence Interval: Computed using Fisher’s z-transformation:

\[\begin{split}z = 0.5 \\ln\\left(\frac{1+r}{1-r}\right)\end{split}\]

References

[1]

Pearson, K. (1896). “Mathematical contributions to the theory of evolution. III. Regression, heredity, and panmixia”. Philosophical Transactions of the Royal Society of London. Series A, 187, 253-318.

[2]

Cohen, J. (1988). Statistical Power Analysis for the Behavioral Sciences (2nd ed.). Routledge.

Examples

>>> # Strong positive correlation
>>> x = np.array([1, 2, 3, 4, 5])
>>> y = np.array([2, 4, 5, 7, 8])
>>> result = test_pearson(x, y)
>>> result['statistic']
0.98...

>>> # With visualization
>>> result, fig = test_pearson(x, y, plot=True)

scitex_stats.test_spearman(x, y, var_x='x', var_y='y', alternative='two-sided', alpha=0.05, plot=False, ax=None, data=None, return_as='dict', decimals=3, verbose=False)

Spearman’s rank correlation coefficient test.

Non-parametric measure of monotonic relationship between two variables. Uses rank-transformed data, more robust to outliers than Pearson.

Parameters:

• x (array-like) – First variable

• y (array-like) – Second variable (same length as x)

• var_x (str, default 'x') – Name of first variable

• var_y (str, default 'y') – Name of second variable

• alternative ({'two-sided', 'less', 'greater'}, default 'two-sided') – Alternative hypothesis: - ‘two-sided’: ρ ≠ 0 - ‘less’: ρ < 0 - ‘greater’: ρ > 0

• alpha (float, default 0.05) – Significance level

• plot (bool, default False) – If True, create visualization with scatter plot of ranks

• data (DataFrame, str, or None, optional) – DataFrame or CSV path. When provided, string values for x/y are resolved as column names (seaborn-style).

• return_as ({'dict', 'dataframe'}, default 'dict') – Return format

• decimals (int, default 3) – Number of decimal places for rounding

Returns:

result – Test results with: - test_method: Name of test - statistic: Spearman’s rho (ρ) - pvalue: p-value - alternative: Alternative hypothesis - alpha: Significance level - significant: Whether result is significant - stars: Significance stars - effect_size: Same as statistic (ρ) - effect_size_metric: ‘rho’ - effect_size_interpretation: Interpretation - rho_squared: Proportion of variance explained - n: Sample size - var_x: First variable name - var_y: Second variable name

Return type:

dict or DataFrame or (dict, Figure)

Notes

Spearman’s ρ is the Pearson correlation of rank-transformed variables.

Assumptions: - Observations are independent - Variables are at least ordinal

Interpretation (same as Pearson): - |ρ| < 0.1: negligible - |ρ| < 0.3: small - |ρ| < 0.5: medium - |ρ| ≥ 0.5: large

References

Spearman, C. (1904). The proof and measurement of association between two things. American Journal of Psychology, 15, 72-101.

Examples

>>> import numpy as np
>>> from scitex_stats.tests.correlation import test_spearman

# Example 1: Perfect monotonic relationship >>> x = np.array([1, 2, 3, 4, 5]) >>> y = np.array([1, 4, 9, 16, 25]) # Quadratic relationship >>> result = test_spearman(x, y, var_x=’x’, var_y=’y²’, plot=True) >>> print(result)

# Example 2: Outlier-robust correlation >>> x = np.array([1, 2, 3, 4, 5, 6, 7, 8, 9, 100]) # Outlier >>> y = np.array([2, 4, 6, 8, 10, 12, 14, 16, 18, 20]) >>> result = test_spearman(x, y, plot=True) >>> print(f”Spearman ρ = {result[‘statistic’]:.3f}, p = {result[‘pvalue’]:.4f}”)

# Example 3: Compare with Pearson >>> from scitex_stats.tests.correlation import test_pearson >>> x = np.random.exponential(scale=2, size=50) >>> y = x + np.random.normal(0, 1, size=50) >>> spearman_result = test_spearman(x, y) >>> pearson_result = test_pearson(x, y) >>> print(f”Spearman: ρ = {spearman_result[‘statistic’]:.3f}”) >>> print(f”Pearson: r = {pearson_result[‘statistic’]:.3f}”)

# Example 4: Ordinal data >>> satisfaction = np.array([1, 2, 3, 4, 5, 1, 2, 3, 4, 5]) >>> quality = np.array([2, 3, 4, 4, 5, 1, 2, 3, 5, 4]) >>> result = test_spearman(satisfaction, quality, … var_x=’Satisfaction’, var_y=’Quality’, … plot=True)

# Example 5: One-tailed test >>> x = np.arange(20) >>> y = x + np.random.normal(0, 2, size=20) >>> result = test_spearman(x, y, alternative=’greater’) >>> print(f”One-tailed p-value: {result[‘pvalue’]:.4f}”)

# Example 6: Non-linear monotonic relationship >>> x = np.linspace(0, 10, 50) >>> y = np.log(x + 1) + np.random.normal(0, 0.1, size=50) >>> result = test_spearman(x, y, var_x=’x’, var_y=’log(x+1)’, plot=True)

# Example 7: Export to various formats >>> result = test_spearman(x, y, return_as=’dataframe’) >>> convert_results(result, return_as=’latex’, path=’spearman.tex’) >>> convert_results(result, return_as=’csv’, path=’spearman.csv’)

scitex_stats.test_kendall(x, y, var_x='x', var_y='y', alternative='two-sided', variant='b', alpha=0.05, plot=False, ax=None, data=None, return_as='dict', decimals=3, verbose=False)

Perform Kendall’s tau correlation test.

Parameters:

• x (array or Series) – First variable

• y (array or Series) – Second variable

• var_x (str, default 'x') – Name for x variable

• var_y (str, default 'y') – Name for y variable

• alternative ({'two-sided', 'less', 'greater'}, default 'two-sided') – Alternative hypothesis: - ‘two-sided’: tau ≠ 0 - ‘less’: tau < 0 (negative association) - ‘greater’: tau > 0 (positive association)

• variant ({'b', 'c'}, default 'b') – Tau variant: - ‘b’: tau-b (Kendall’s tau-b, accounts for ties) - ‘c’: tau-c (Stuart’s tau-c, for contingency tables)

• alpha (float, default 0.05) – Significance level

• plot (bool, default False) – Whether to generate scatter plot

• ax (matplotlib.axes.Axes, optional) – Axes to plot on. If provided, plot is set to True

• data (DataFrame, str, or None, optional) – DataFrame or CSV path. When provided, string values for x/y are resolved as column names (seaborn-style).

• return_as ({'dict', 'dataframe'}, default 'dict') – Output format

• decimals (int, default 3) – Number of decimal places for rounding

• verbose (bool, default False) – If True, print test results to logger

Returns:

result – Test results including: - test_method: Name of test - statistic: Kendall’s tau coefficient - pvalue: p-value - tau_squared: tau² (proportion of variance explained) - effect_size: tau (same as statistic) - effect_size_interpretation: interpretation - n: Sample size - n_concordant: Number of concordant pairs - n_discordant: Number of discordant pairs - n_ties: Number of tied pairs - significant: Whether to reject null hypothesis - stars: Significance stars

Return type:

dict or DataFrame

Notes

Kendall’s tau is a non-parametric measure of monotonic association between two variables. It is based on concordant and discordant pairs.

Null Hypothesis (H0): No monotonic association (tau = 0)

Alternative Hypothesis (H1): Monotonic association exists

Concordant vs Discordant Pairs: For pairs (x_i, y_i) and (x_j, y_j): - Concordant: (x_i < x_j and y_i < y_j) or (x_i > x_j and y_i > y_j) - Discordant: (x_i < x_j and y_i > y_j) or (x_i > x_j and y_i < y_j)

Kendall’s tau-b (accounts for ties):

\[\begin{split}\tau_b = \frac{n_c - n_d}{\\sqrt{(n_0 - n_1)(n_0 - n_2)}}\end{split}\]

Where: - n_c: Number of concordant pairs - n_d: Number of discordant pairs - n_0: n(n-1)/2 (total possible pairs) - n_1: Sum of t_i(t_i-1)/2 for ties in x - n_2: Sum of u_j(u_j-1)/2 for ties in y

Interpretation: - tau = 1: Perfect positive association - tau = 0: No association - tau = -1: Perfect negative association

Effect size interpretation (same as correlation): - |tau| < 0.1: negligible - |tau| < 0.3: small - |tau| < 0.5: medium - |tau| ≥ 0.5: large

Advantages over Spearman: - More robust to outliers - Better for small samples - Better interpretation (probability of concordance) - More accurate p-values with ties

Disadvantages: - Computationally more expensive (O(n²)) - Generally smaller magnitude than Spearman’s rho - Less intuitive interpretation than Pearson

When to use Kendall’s tau: - Small sample sizes (n < 30) - Data with many ties - Ordinal data - Non-normal data with outliers

Examples

>>> import numpy as np
>>> from scitex_stats.tests.correlation import test_kendall
>>>
>>> # Monotonic relationship with ties
>>> x = np.array([1, 2, 2, 3, 4, 4, 5, 6, 7])
>>> y = np.array([2, 3, 3, 5, 6, 6, 8, 9, 10])
>>>
>>> result = test_kendall(x, y, var_x='Treatment Dose', var_y='Response',
...                       plot=True)
>>> print(f"τ = {result['statistic']:.3f}, p = {result['pvalue']:.4f}")
>>> print(f"Concordant pairs: {result['n_concordant']}")

References

[1]

Kendall, M. G. (1938). “A New Measure of Rank Correlation”. Biometrika, 30(1/2), 81-93.

[2]

Kendall, M. G. (1945). “The treatment of ties in ranking problems”. Biometrika, 33(3), 239-251.

See also

test_spearman

Alternative rank correlation

test_pearson

Parametric correlation

scitex_stats.test_theilsen(x, y, var_x='x', var_y='y', data=None, return_as='dict', verbose=True)

Theil-Sen robust regression estimator.

A robust non-parametric regression method that estimates the slope as the median of all pairwise slopes. Highly resistant to outliers (up to 29.3% breakdown point).

Parameters:

• x (array-like) – Independent variable

• y (array-like) – Dependent variable

• var_x (str, default="x") – Name of independent variable (for reporting)

• var_y (str, default="y") – Name of dependent variable (for reporting)

• data (DataFrame, str, or None, optional) – DataFrame or CSV path. When provided, string values for x/y are resolved as column names (seaborn-style).

• return_as (str, default="dict") – Format of return value: “dict” or “dataframe”

• verbose (bool, default=True) – Whether to print results

Returns:

Dictionary or DataFrame containing: - slope : float

Theil-Sen slope estimate (median of pairwise slopes)

• interceptfloat

  Intercept of the regression line

• low_slopefloat

  Lower bound of slope confidence interval

• high_slopefloat

  Upper bound of slope confidence interval

• var_xstr

  Name of independent variable

• var_ystr

  Name of dependent variable

Return type:

dict or pd.DataFrame

Notes

The Theil-Sen estimator: - Is robust to outliers (up to ~29% outliers) - Has no distributional assumptions - Is asymptotically normal - Has ~64% efficiency compared to OLS for normal data - Computational complexity: O(n²)

References

[1]

Theil, H. (1950). “A rank-invariant method of linear and polynomial regression analysis”. Indagationes Mathematicae, 12, 85-91.

[2]

Sen, P.K. (1968). “Estimates of the regression coefficient based on Kendall’s tau”. Journal of the American Statistical Association, 63, 1379-1389.

Examples

>>> import numpy as np
>>> from scitex_stats.tests.correlation import test_theilsen
>>> x = np.array([1, 2, 3, 4, 5])
>>> y = np.array([2, 4, 6, 8, 10])
>>> result = test_theilsen(x, y, verbose=False)
>>> print(f"Slope: {result['slope']:.3f}")
Slope: 2.000

>>> # With outlier
>>> y_outlier = np.array([2, 4, 6, 8, 100])  # One extreme outlier
>>> result = test_theilsen(x, y_outlier, verbose=False)
>>> print(f"Robust slope: {result['slope']:.3f}")
Robust slope: 2.000

scitex_stats.test_chi2(observed, var_row=None, var_col=None, alpha=0.05, correction=True, plot=False, ax=None, return_as='dict', decimals=3, verbose=False)

Chi-square test of independence for contingency tables.

Tests whether two categorical variables are independent.

Parameters:

• observed (array-like or DataFrame) – Observed frequencies as contingency table (rows × columns) If DataFrame, row/column names used as variable names

• var_row (str, optional) – Name of row variable (default: ‘row_variable’)

• var_col (str, optional) – Name of column variable (default: ‘col_variable’)

• alpha (float, default 0.05) – Significance level

• correction (bool, default True) – Apply Yates’ continuity correction for 2×2 tables

• plot (bool, default False) – If True, create mosaic plot visualization

• ax (matplotlib.axes.Axes, optional) – Axes to plot on. If provided, plot is set to True

• return_as ({'dict', 'dataframe'}, default 'dict') – Return format

• decimals (int, default 3) – Number of decimal places for rounding

• verbose (bool, default False) – If True, print test results to logger

Returns:

result – Test results with: - test_method: Name of test - statistic: Chi-square statistic (χ²) - pvalue: p-value - df: Degrees of freedom - alpha: Significance level - significant: Whether result is significant - stars: Significance stars - effect_size: Cramér’s V - effect_size_metric: “Cramér’s V” - effect_size_interpretation: Interpretation - n: Total sample size - expected_min: Minimum expected frequency - var_row: Row variable name - var_col: Column variable name

Return type:

dict or DataFrame

Notes

Chi-square test of independence tests: H₀: Two categorical variables are independent H₁: Two categorical variables are associated

Test statistic: χ² = Σ[(O - E)² / E] where O = observed frequencies, E = expected frequencies

Assumptions: 1. Independence of observations 2. Expected frequencies ≥ 5 in at least 80% of cells 3. No expected frequencies < 1

For 2×2 tables with small expected frequencies, use Fisher’s exact test instead.

Cramér’s V measures strength of association (0 to 1): - 0 = no association - 1 = perfect association

References

Cramér, H. (1946). Mathematical Methods of Statistics. Princeton University Press.

Examples

>>> import numpy as np
>>> from scitex_stats.tests.categorical import test_chi2

# Example 1: 2×2 contingency table (treatment × outcome) >>> observed = np.array([[30, 10], [20, 40]]) >>> result = test_chi2(observed, var_row=’Treatment’, var_col=’Outcome’, plot=True) >>> print(result)

# Example 2: Using DataFrame >>> import pandas as pd >>> df = pd.DataFrame([[12, 8, 5], [15, 20, 10]], … index=[‘Group A’, ‘Group B’], … columns=[‘Low’, ‘Med’, ‘High’]) >>> result = test_chi2(df, plot=True)

# Example 3: Test gender × preference association >>> observed = np.array([ … [20, 30, 15], # Male: product A, B, C … [25, 20, 40] # Female: product A, B, C … ]) >>> result = test_chi2(observed, var_row=’Gender’, var_col=’Product’, plot=True) >>> print(f”χ² = {result[‘statistic’]:.2f}, p = {result[‘pvalue’]:.4f}”) >>> print(f”Cramér’s V = {result[‘effect_size’]:.3f} ({result[‘effect_size_interpretation’]})”)

# Example 4: Small expected frequencies warning >>> observed = np.array([[2, 8], [3, 7]]) # Small counts >>> result = test_chi2(observed)

# Example 5: Export to various formats >>> result = test_chi2(observed, return_as=’dataframe’) >>> convert_results(result, return_as=’latex’, path=’chi2_test.tex’)

scitex_stats.test_fisher(observed, var_row=None, var_col=None, alternative='two-sided', alpha=0.05, plot=False, ax=None, return_as='dict', decimals=3, verbose=False)

Fisher’s exact test for 2×2 contingency tables.

Tests association between two binary categorical variables. Exact test (no large-sample approximation required).

Parameters:

• observed (array-like or DataFrame) – 2×2 contingency table as [[a, b], [c, d]] If DataFrame, row/column names used as variable names

• var_row (str, optional) – Name of row variable (default: ‘row_variable’)

• var_col (str, optional) – Name of column variable (default: ‘col_variable’)

• alternative ({'two-sided', 'less', 'greater'}, default 'two-sided') – Alternative hypothesis: - ‘two-sided’: odds ratio ≠ 1 - ‘less’: odds ratio < 1 - ‘greater’: odds ratio > 1

• alpha (float, default 0.05) – Significance level for confidence interval

• plot (bool, default False) – If True, create visualization

• ax (matplotlib.axes.Axes, optional) – Axes to plot on. If provided, plot is set to True

• return_as ({'dict', 'dataframe'}, default 'dict') – Return format

• decimals (int, default 3) – Number of decimal places for rounding

• verbose (bool, default False) – If True, print test results to logger

Returns:

result – Test results with: - test_method: Name of test - statistic: Odds ratio - pvalue: Exact p-value - alternative: Alternative hypothesis - alpha: Significance level - significant: Whether result is significant - stars: Significance stars - effect_size: Odds ratio - effect_size_metric: ‘Odds ratio’ - effect_size_interpretation: Interpretation - ci_lower: Lower CI bound for odds ratio - ci_upper: Upper CI bound for odds ratio - n: Total sample size - var_row: Row variable name - var_col: Column variable name

Return type:

dict or DataFrame

Notes

Fisher’s exact test computes exact probability of observed table (and more extreme tables) under independence assumption.

H₀: Two binary variables are independent (OR = 1) H₁: Variables are associated (OR ≠ 1)

Odds Ratio (OR): For table [[a, b], [c, d]]: OR = (a × d) / (b × c)

Interpretation: - OR = 1: No association - OR > 1: Positive association - OR < 1: Negative association

When to use: - 2×2 contingency tables - Small sample sizes (any cell < 5) - Need exact p-value (not approximation)

Advantages over chi-square: - Exact test (valid for any sample size) - No minimum expected frequency requirement - More powerful for small samples

References

Fisher, R. A. (1922). On the interpretation of χ² from contingency tables, and the calculation of P. Journal of the Royal Statistical Society, 85(1), 87-94.

Examples

>>> import numpy as np
>>> from scitex_stats.tests.categorical import test_fisher

# Example 1: Small 2×2 table (treatment × outcome) >>> observed = [[8, 2], [1, 5]] >>> result = test_fisher(observed, var_row=’Treatment’, var_col=’Response’, plot=True) >>> print(result)

# Example 2: Case-control study >>> exposed_cases = 12 >>> unexposed_cases = 5 >>> exposed_controls = 8 >>> unexposed_controls = 20 >>> observed = [[exposed_cases, unexposed_cases], … [exposed_controls, unexposed_controls]] >>> result = test_fisher(observed, var_row=’Exposure’, var_col=’Disease’) >>> print(f”OR = {result[‘statistic’]:.2f}, 95% CI [{result[‘ci_lower’]:.2f}, {result[‘ci_upper’]:.2f}]”) >>> print(f”p = {result[‘pvalue’]:.4f}”)

# Example 3: One-tailed test (expect positive association) >>> observed = [[10, 2], [3, 8]] >>> result = test_fisher(observed, alternative=’greater’) >>> print(f”One-tailed p = {result[‘pvalue’]:.4f}”)

# Example 4: Using pandas DataFrame >>> import pandas as pd >>> df = pd.DataFrame([[15, 5], [3, 10]], … index=[‘Group A’, ‘Group B’], … columns=[‘Success’, ‘Failure’]) >>> result = test_fisher(df, plot=True)

# Example 5: Compare with chi-square >>> from scitex_stats.tests.categorical import test_chi2 >>> observed = [[5, 10], [10, 5]] >>> fisher_result = test_fisher(observed) >>> chi2_result = test_chi2(observed) >>> print(f”Fisher’s exact p = {fisher_result[‘pvalue’]:.4f}”) >>> print(f”Chi-square p = {chi2_result[‘pvalue’]:.4f}”)

scitex_stats.test_mcnemar(observed, var_before=None, var_after=None, correction=True, alpha=0.05, plot=False, ax=None, return_as='dict', decimals=3, verbose=False)

Perform McNemar’s test for paired categorical data.

Tests whether there is a significant change in proportions for paired binary data. Appropriate for before-after studies with binary outcomes.

Parameters:

• observed (array-like, shape (2, 2)) –

  2×2 contingency table: [[a, b],

  [c, d]]

  where: - a: both conditions negative (0,0) - b: before negative, after positive (0,1) - c: before positive, after negative (1,0) - d: both conditions positive (1,1)

• var_before (str, optional) – Name for before condition

• var_after (str, optional) – Name for after condition

• correction (bool, default True) – Whether to apply continuity correction (recommended for small samples)

• alpha (float, default 0.05) – Significance level

• plot (bool, default False) – Whether to generate visualization

• ax (matplotlib.axes.Axes, optional) – Axes to plot on. If provided, plot is set to True

• return_as ({'dict', 'dataframe'}, default 'dict') – Output format

• decimals (int, default 3) – Number of decimal places for rounding

• verbose (bool, default False) – If True, print test results to logger

Returns:

result – Test results including: - test_method: Name of test - statistic: χ² statistic - pvalue: p-value - df: degrees of freedom (always 1) - b: count of (before=0, after=1) - c: count of (before=1, after=0) - odds_ratio: b / c - effect_size: odds ratio - effect_size_interpretation: interpretation - significant: whether to reject null hypothesis - stars: significance stars

Return type:

dict or DataFrame

Notes

McNemar’s test is used for paired nominal data, testing whether row and column marginal frequencies are equal (marginal homogeneity).

The test statistic is based on the discordant pairs (b and c):

\[\begin{split}\\chi^2 = \\frac{(b - c)^2}{b + c} \\quad \\text{(without correction)}\end{split}\]

\[\begin{split}\\chi^2 = \\frac{(|b - c| - 1)^2}{b + c} \\quad \\text{(with correction)}\end{split}\]

Null hypothesis: The marginal proportions are equal (no change) Alternative: The marginal proportions differ (significant change)

Assumptions: - Paired data (matched observations) - Binary outcomes for both conditions - Large enough sample (b + c ≥ 10 recommended for chi-square approximation)

Effect size (Odds Ratio): OR = b / c - OR = 1: no change - OR > 1: increase (more transitions from 0→1 than 1→0) - OR < 1: decrease (more transitions from 1→0 than 0→1)

Examples

>>> import numpy as np
>>> from scitex_stats.tests.categorical import test_mcnemar
>>>
>>> # Example: Treatment effectiveness (before/after)
>>> # Rows: before, Columns: after
>>> # [[no→no, no→yes],
>>> #  [yes→no, yes→yes]]
>>> observed = [[59, 6],   # 59 stayed negative, 6 improved
...             [16, 19]]  # 16 relapsed, 19 stayed positive
>>>
>>> result = test_mcnemar(observed, var_before='Before Treatment',
...                       var_after='After Treatment', plot=True)
>>> print(f"χ² = {result['statistic']:.2f}, p = {result['pvalue']:.4f}")
>>> print(f"Odds Ratio = {result['odds_ratio']:.2f}")

References

[1]

McNemar, Q. (1947). “Note on the sampling error of the difference between correlated proportions or percentages”. Psychometrika, 12(2), 153-157.

[2]

Edwards, A. L. (1948). “Note on the correction for continuity in testing the significance of the difference between correlated proportions”. Psychometrika, 13(3), 185-187.

See also

test_chi2

For independent (unpaired) categorical data

test_fisher

For 2×2 tables with small expected frequencies

scitex_stats.test_cochran_q(data, subject_col=None, condition_col=None, value_col=None, condition_names=None, alpha=0.05, plot=False, return_as='dict', decimals=3)

Perform Cochran’s Q test for binary repeated measures.

Extension of McNemar’s test to 3+ conditions. Tests whether proportions of successes differ across multiple related binary measurements.

Parameters:

• data (array or DataFrame) –

  • If array: shape (n_subjects, n_conditions), wide format with 0/1 values

  • If DataFrame with subject_col/condition_col: long format

  • If DataFrame without: wide format (rows=subjects, cols=conditions)

• subject_col (str, optional) – Column name for subject IDs (long format)

• condition_col (str, optional) – Column name for conditions (long format)

• value_col (str, optional) – Column name for binary values (long format)

• condition_names (list of str, optional) – Names for conditions (wide format)

• alpha (float, default 0.05) – Significance level

• plot (bool, default False) – Whether to generate visualization

• return_as ({'dict', 'dataframe'}, default 'dict') – Output format

• decimals (int, default 3) – Number of decimal places for rounding

Return type:

Union[dict, DataFrame, Tuple]

Returns:

• result (dict or DataFrame) – Test results including: - statistic: Cochran’s Q statistic - pvalue: p-value - df: Degrees of freedom (k - 1) - effect_size: Kendall’s W - effect_size_interpretation: interpretation - n_subjects: Number of subjects - n_conditions: Number of conditions - proportions: Success proportion for each condition - n_successes: Number of successes per condition - significant: Whether to reject null hypothesis - stars: Significance stars

• If plot=True, returns tuple of (result, figure)

Notes

Cochran’s Q test is used for repeated binary measurements (dichotomous data) on the same subjects across 3+ conditions.

Null Hypothesis (H0): Proportions of successes are equal across conditions

Alternative Hypothesis (H1): At least one proportion differs

Test Statistic:

\[\begin{split}Q = \\frac{(k-1)[k\\sum_{j=1}^{k}G_j^2 - N^2]}{k\\sum_{i=1}^{n}L_i - \\sum_{i=1}^{n}L_i^2} # noqa: D301\end{split}\]

Where: - k: Number of conditions - n: Number of subjects - G_j: Number of successes in condition j - L_i: Number of successes for subject i (across conditions) - N: Total number of successes

Q follows chi-square distribution with k-1 degrees of freedom.

Effect Size (Kendall’s W for binary):

\[\begin{split}W = \\frac{\\sum_{j=1}^{k}(G_j - \\bar{G})^2}{n(k-1)k/12} # noqa: D301\end{split}\]

Interpretation: - W < 0.1: negligible - W < 0.3: small - W < 0.5: medium - W ≥ 0.5: large

Assumptions: - Binary outcomes (0/1, success/failure, yes/no) - Repeated measurements on same subjects - At least 3 conditions (for 2 conditions, use McNemar’s test)

Relation to other tests: - Extension of McNemar’s test (2 conditions → 3+ conditions) - Binary version of Friedman test - Can use Friedman test on same data (Q ≈ Friedman χ²)

Post-hoc tests: If significant: - Pairwise McNemar tests - Apply corrections: correct_bonferroni(), correct_holm()

Advantages: - Appropriate for binary repeated measures - No normality assumption - Accounts for within-subject correlation

Disadvantages: - Requires binary data - Sensitive to subjects with all 0s or all 1s - Less powerful than parametric alternatives if assumptions met

Examples

>>> import numpy as np
>>> from scitex_stats.tests.categorical import test_cochran_q
>>>
>>> # Example: Treatment success (0=fail, 1=success) across 4 visits
>>> data = np.array([
...     [0, 0, 1, 1],  # Subject 1: improved over time
...     [0, 1, 1, 1],  # Subject 2: improved
...     [0, 0, 0, 1],  # Subject 3: late improvement
...     [1, 1, 1, 1],  # Subject 4: always success
...     [0, 0, 1, 1],  # Subject 5: improved
... ])
>>>
>>> result = test_cochran_q(
...     data,
...     condition_names=['Visit 1', 'Visit 2', 'Visit 3', 'Visit 4'],
...     plot=True
... )
>>>
>>> print(f"Q = {result['statistic']:.2f}, p = {result['pvalue']:.4f}")
>>> print(f"Proportions: {result['proportions']}")

References

[1]

Cochran, W. G. (1950). “The comparison of percentages in matched samples”. Biometrika, 37(3/4), 256-266.

[2]

McNemar, Q. (1947). “Note on the sampling error of the difference between correlated proportions or percentages”. Psychometrika, 12(2), 153-157.

See also

test_mcnemar

For 2 binary conditions

test_friedman

Non-parametric repeated measures (non-binary)

scitex_stats.test_shapiro(x, var_x='x', alpha=0.05, plot=False, ax=None, data=None, return_as='dict', verbose=False)

Perform Shapiro-Wilk test for normality.

Parameters:

• x (array or Series) – Sample to test

• var_x (str, default 'x') – Label for sample

• alpha (float, default 0.05) – Significance level

• plot (bool, default False) – Whether to generate Q-Q plot

• ax (matplotlib.axes.Axes, optional) – Axes to plot on. If provided, plot is set to True

• data (DataFrame, str, or None, optional) – DataFrame or CSV path. When provided, string value for x is resolved as a column name (seaborn-style).

• return_as ({'dict', 'dataframe'}, default 'dict') – Output format

• verbose (bool, default False) – If True, print test results to logger

Returns:

results – Test results including: - test_method: ‘Shapiro-Wilk test’ - statistic: W-statistic value (0 to 1, closer to 1 = more normal) - pvalue: p-value - stars: Significance stars - significant: Whether null hypothesis is rejected (True = not normal) - normal: Whether data appears normal (True = normal) - recommendation: Suggested statistical approach - n: Sample size - var_x: Variable label

Return type:

dict or DataFrame

Notes

The Shapiro-Wilk test tests the null hypothesis that data come from a normal distribution.

Null Hypothesis (H0): Data are normally distributed

Test Statistic W: Ranges from 0 to 1 - W close to 1: Data appear normal - W much less than 1: Data deviate from normality

p-value interpretation: - p > α (typically 0.05): Fail to reject H0, data appear normal - p ≤ α: Reject H0, data significantly deviate from normality

Important considerations: - Sensitive to sample size: with n > 50, may detect trivial deviations - Works best for 3 ≤ n ≤ 5000 - Should be combined with visual inspection (Q-Q plots) - Large samples: focus on Q-Q plots over p-values - Small samples: test may lack power to detect non-normality

Recommendations based on results: - Normal (p > 0.05): Use parametric tests (t-test, ANOVA, Pearson) - Non-normal (p ≤ 0.05): Use non-parametric tests (Brunner-Munzel, Wilcoxon, Spearman) - Borderline: Check Q-Q plot and consider robustness

References

[1]

Shapiro, S. S., & Wilk, M. B. (1965). “An analysis of variance test for normality (complete samples)”. Biometrika, 52(3-4), 591-611.

[2]

Razali, N. M., & Wah, Y. B. (2011). “Power comparisons of Shapiro-Wilk, Kolmogorov-Smirnov, Lilliefors and Anderson-Darling tests”. Journal of Statistical Modeling and Analytics, 2(1), 21-33.

Examples

>>> # Normal data
>>> x = np.random.normal(0, 1, 100)
>>> result = test_shapiro(x)
>>> result['normal']
True

>>> # Non-normal data
>>> x = np.random.exponential(2, 100)
>>> result = test_shapiro(x)
>>> result['normal']
False

>>> # With Q-Q plot
>>> result, fig = test_shapiro(x, plot=True)

scitex_stats.test_normality(*samples, var_names=None, alpha=0.05, warn=True)

Check normality for multiple samples using Shapiro-Wilk test.

Parameters:

• *samples (arrays) – Samples to check

• var_names (list of str, optional) – Names for each sample

• alpha (float, default 0.05) – Significance level

• warn (bool, default True) – Whether to log warnings for non-normal data

Returns:

Dictionary with results for each sample: - ‘all_normal’: bool, True if all samples are normal - ‘results’: list of individual test results - ‘recommendation’: str, overall recommendation

Return type:

dict

Examples

>>> x = np.random.normal(0, 1, 50)
>>> y = np.random.exponential(2, 50)
>>> check = check_normality(x, y, var_names=['Normal', 'Exponential'])
>>> check['all_normal']
False
>>> check['recommendation']
'Some samples deviate from normality. Consider non-parametric tests.'

scitex_stats.test_ks_1samp(x, cdf='norm', args=(), var_x='x', alternative='two-sided', alpha=0.05, plot=False, ax=None, data=None, return_as='dict', decimals=3, verbose=False)

Perform one-sample Kolmogorov-Smirnov test.

Parameters:

• x (array or Series) – Sample to test

• cdf (str or callable, default 'norm') – Reference distribution. Either: - String: ‘norm’, ‘uniform’, ‘expon’, etc. (scipy.stats distribution name) - Callable: CDF function

• args (tuple, default ()) – Distribution parameters (e.g., (loc, scale) for normal)

• var_x (str, default 'x') – Label for sample

• alternative ({'two-sided', 'less', 'greater'}, default 'two-sided') – Alternative hypothesis

• alpha (float, default 0.05) – Significance level

• plot (bool, default False) – Whether to generate CDF comparison plot

• data (DataFrame, str, or None, optional) – DataFrame or CSV path. When provided, string value for x is resolved as a column name (seaborn-style).

• return_as ({'dict', 'dataframe'}, default 'dict') – Output format

• decimals (int, default 3) – Number of decimal places for rounding

Return type:

Union[dict, DataFrame]

Returns:

• results (dict or DataFrame) – Test results including: - test_method: ‘Kolmogorov-Smirnov test (1-sample)’ - statistic_name: ‘D’ - statistic: KS D-statistic (maximum CDF difference) - pvalue: p-value - pstars: Significance stars - rejected: Whether null hypothesis is rejected - n_x: Sample size - var_x: Variable label - reference_distribution: Name of reference distribution - H0: Null hypothesis description

• fig (matplotlib.figure.Figure, optional) – Figure with CDF comparison (only if plot=True)

Notes

The one-sample Kolmogorov-Smirnov test compares the empirical cumulative distribution function (ECDF) of the sample against a reference CDF.

Null Hypothesis (H0): Data follow the specified distribution

Test Statistic D:

\[\begin{split}D = \\sup_x |F_n(x) - F(x)|\end{split}\]

Where: - F_n(x): Empirical CDF of sample - F(x): Reference CDF

Advantages: - Distribution-free (no assumptions about data) - Can test against any continuous distribution - More general than Shapiro-Wilk (not limited to normality)

Disadvantages: - Less powerful than Shapiro-Wilk for normality testing - Sensitive to sample size (large n → high power, may detect trivial deviations) - Assumes continuous distribution (not suitable for discrete data)

When to use: - Testing goodness-of-fit to any continuous distribution - Comparing sample to theoretical distribution - When Shapiro-Wilk is not applicable (non-normal distributions) - Large sample sizes (n > 50)

References

[1]

Kolmogorov, A. (1933). “Sulla determinazione empirica di una legge di distribuzione”. Giornale dell’Istituto Italiano degli Attuari, 4, 83-91.

[2]

Smirnov, N. (1948). “Table for estimating the goodness of fit of empirical distributions”. Annals of Mathematical Statistics, 19(2), 279-281.

Examples

>>> # Test if data are normally distributed
>>> x = np.random.normal(0, 1, 100)
>>> result = test_ks_1samp(x, cdf='norm', args=(0, 1))
>>> result['rejected']
False

>>> # Test if data are uniformly distributed
>>> x = np.random.uniform(0, 1, 100)
>>> result = test_ks_1samp(x, cdf='uniform', args=(0, 1))

scitex_stats.test_ks_2samp(x, y, var_x='x', var_y='y', alternative='two-sided', alpha=0.05, plot=False, ax=None, data=None, return_as='dict', decimals=3, verbose=False)

Perform two-sample Kolmogorov-Smirnov test.

Parameters:

• x (arrays or Series) – Two samples to compare

• y (arrays or Series) – Two samples to compare

• var_x (str) – Labels for samples

• var_y (str) – Labels for samples

• alternative ({'two-sided', 'less', 'greater'}, default 'two-sided') – Alternative hypothesis

• alpha (float, default 0.05) – Significance level

• plot (bool, default False) – Whether to generate CDF comparison plot

• data (DataFrame, str, or None, optional) – DataFrame or CSV path. When provided, string values for x/y are resolved as column names (seaborn-style).

• return_as ({'dict', 'dataframe'}, default 'dict') – Output format

• decimals (int, default 3) – Number of decimal places for rounding

Return type:

Union[dict, DataFrame]

Returns:

• results (dict or DataFrame) – Test results including: - test_method: ‘Kolmogorov-Smirnov test (2-sample)’ - statistic_name: ‘D’ - statistic: KS D-statistic - pvalue: p-value - pstars: Significance stars - rejected: Whether null hypothesis is rejected - n_x, n_y: Sample sizes - var_x, var_y: Variable labels - H0: Null hypothesis description

• fig (matplotlib.figure.Figure, optional) – Figure with CDF comparison (only if plot=True)

Notes

The two-sample Kolmogorov-Smirnov test compares the ECDFs of two samples.

Null Hypothesis (H0): Both samples come from the same distribution

Test Statistic D:

\[\begin{split}D = \\sup_x |F_{n_1}(x) - F_{n_2}(x)|\end{split}\]

Where F_{n_1} and F_{n_2} are the empirical CDFs.

Advantages: - Distribution-free (non-parametric) - Tests entire distribution, not just location - Can detect differences in location, scale, or shape

Disadvantages: - Less powerful than t-test when assumptions are met - Most sensitive to differences near the center of distributions - Less sensitive to tail differences

When to use: - Comparing two independent samples - No assumptions about distribution shape - Want to test overall distribution equality (not just means) - Alternative to t-test when normality violated

Comparison with other tests: - vs t-test: More robust, less powerful - vs Mann-Whitney U: Tests different hypotheses (distribution vs median) - vs Brunner-Munzel: KS tests full distribution, BM tests P(X>Y)

Examples

>>> # Two samples from same distribution
>>> x = np.random.normal(0, 1, 100)
>>> y = np.random.normal(0, 1, 100)
>>> result = test_ks_2samp(x, y)
>>> result['rejected']
False

>>> # Two samples from different distributions
>>> x = np.random.normal(0, 1, 100)
>>> y = np.random.normal(2, 1, 100)
>>> result = test_ks_2samp(x, y)
>>> result['rejected']
True

scitex_stats._PackageNotFoundError

alias of PackageNotFoundError

scitex_stats._version(distribution_name)

Get the version string for the named package.

Parameters:

distribution_name – The name of the distribution package to query.

Returns:

The version string for the package as defined in the package’s “Version” metadata key.