fn wilcoxon_one_sided(deltas: &[f64]) -> Option<f64>Expand description
One-sided Wilcoxon signed-rank p for “the deltas are positive”.
Textbook construction: zeros dropped, absolute deltas ranked with average
ranks over ties, W⁻ (the rank sum of the negative deltas) compared
against its null distribution by normal approximation with the tie
correction and a continuity correction. Small W⁻ — losses carrying
little rank weight — yields small p.
None when fewer than WILCOXON_MIN_PAIRS non-zero deltas remain.