Mann–Whitney U and Wilcoxon Signed‐Rank

The Mann-Whitney U test and the Wilcoxon signed-rank test are both commonly used two-sample nonparametric statistical tests. This chapter elaborates on the main principles for both tests. The Mann-Whitney U test and Wilcoxon signed-rank test are most applicable when the following assumptions are fulfilled: data type; distribution of data; sampling groups and observations; equal sample sizes; and random sampling. The Mann-Whitney U and the Wilcoxon signed-rank tests share similar hypotheses. In general, the hypotheses compare the median for population A to that of population B and evaluate differences between the populations. The null hypothesis (H0) states that the two samples come from the same population, indicating no difference. Statistical programs are used in the chapter to run a Mann-Whitney U and a Wilcoxon signed-rank test and determine the significance, or p-value, for a statistical analysis.