nonparam
Wilcoxon signed-rank
Compare paired ordinal or non-normal continuous measurements.
Requirements
- paired observations
- signed non-zero differences
Avoid when
- independent groups
- many zero differences
Formula
W = Σ rank(|dᵢ|) · sign(dᵢ)
Interpretation
Tests whether paired differences are centered at zero.
Worked example
Compare paired pain ratings before and after an intervention using ranks.
Open example datasets