As the Wilcoxon signed-ranks test does not assume normality of the differences of the two related groups, it can be used when this assumption has been violated and the use of the paired t-test is inappropriate.įor example, you could use a Wilcoxon signed-rank test to determine whether there is a difference in the number of customer complaints before and after a training course for sales reps designed to improve their customer interactions (i.e., the dependent variable would be “customer complaints”, and the two related groups would be the two different “time points” that is, the number of customer complaints “before” the training course and the number of customer complaints “after“ the training course. It is the nonparametric equivalent to the paired t-test. The Wilcoxon signed-rank test determines whether there is a statistically significant difference in the median of a dependent variable between two related groups. Wilcoxon signed-rank test using Minitab Introduction