Wilcoxon Signed-Rank Test

The Wilcoxon signed-rank test is a non-parametric alternative to the paired t-test, used to compare two related samples when the data are ordinal or not normally distributed. It ranks the absolute differences between paired observations and tests whether the sum of positive and negative ranks differs significantly from zero. In accessibility research it is commonly used for pairwise post-hoc comparisons after a significant Friedman test, with a Bonferroni correction applied to control the family-wise error rate across multiple comparisons.