Wilcoxon Rank-sum Test
- This is used to test the hypothesis that two independent samples have come from the same population. Because it is non-parametric, it makes only limited assumptions about the distribution of the data. The method employed is a sum-of-ranks comparison. It is an alternative to the two-sample t-test, and is based only on the order in which the observations from the two samples fall. It is of evident use when data are ordinal in nature and a comparison of means is meaningless.