Rank sum test (for two unpaired Samples) from Wilcoxon

H0: The two distributions of X und Y are equal
H1: The two distributions of X und Y are different

Remark:
The distributions are FX and FY, where FX is the distribution of  X1, ..., Xm and  FY is the distribution of Y1, ..., Yn.



             
sample 1 (xi)sample 2 (yi)