6.5.1 The Mann-Whitney U Test and Wilcoxon Signed-Rank Test

The Mann-Whitney U test (also known as the Wilcoxon rank-sum test) is the non-parametric analogue of the unpaired t-test, comparing the rank distributions...

The Mann-Whitney U test (also known as the Wilcoxon rank-sum test) is the non-parametric analogue of the unpaired t-test, comparing the rank distributions of two independent groups rather than their means; it is appropriate when comparing, for example, two independent groups of animals with a non-normally distributed or ordinal outcome. The Wilcoxon signed-rank test serves the analogous role for paired data, comparing the ranked magnitude and direction of within-subject differences between two paired conditions, such as a physiological measurement taken in the same animals before and after treatment.