ADD:

ruff for code formatting

BIC statistic AND BIC test implemented

test_distributions.py for test new created dists with pytest

REFACTOR:
k_gen pdf changed from 2 params to generalized

etc/tools/statistics.py

@@ -16,3 +16,20 @@ def aic_statistic(dist, data, axis):
     aic = 2 * k - 2 * log_likelihood
 
     return aic
+
+def bic_statistic(dist, data, axis):
+    """
+    BIC-based goodness-of-fit statistic.
+
+    BIC = ln(n)k - 2ln(L)s
+
+    Lower BIC indicates better fit, but since goodness_of_fit()
+    treats larger statistic values as worse fit, BIC works directly.
+    """
+
+    n = data.size if axis is None else data.shape[axis]
+    k = len(dist.args)
+    log_likelihood = np.sum(dist.logpdf(data), axis=axis)
+    bic = np.log(n) * k - 2 * log_likelihood
+
+    return bic