A Mann-Whitney test indicates whether values tend to be larger in one of two columns. If the values are drawn from distributions having the same shape but different locations, the Mann-Whitney test can be interpreted as a test of whether the column medians are equal.
To perform a Mann-Whitney test:
Note that even if the observed medians are equal across categories, the Mann-Whitney test can indicate that the population medians are not equal. This is most likely due to the distribution of values differing across columns.
To analyze differences in three or more numeric columns’ medians, use a Kruskal-Wallis test.