I have data from 4 populations : A (n=16), B (n=16), C (n=14) and D (n=16).
Data from A and B are not normally distributed. Data from C and D are normally distributed. All data passed the Levene's test for equality of variance. Kruskal-Wallis test does not show any differences between group.
The independent Mann-Whitney test gave significant results when comparing A and C, but not when comparing A and D, although the median differences between A and D were greater than those between A and C.
I am not familiar with stat, and very confused by the results. Could you please help me to understand ?