Examples for probability distributions of Wilcoxon rank sum tests. Data were obtained where resampling size, n, equaled to 6 (100 iterations). Assessment of significance was based on p-values obtained from the Kolmogorov-Smirnov test between test and random distributions (pt and pr1, respectively). (A, C) For test data, GSN gene had a highly significant differential expression (significant at 100% of iterations, p = 0.00) between ductal and normal samples whereas RAP2A gene did not (significant at 5% of iterations, p = 0.98). (B, D) Probability values of both GSN and RAP2A, obtained from randomized data, were uniformly distributed. GSN; IMAGE: 214990 and RAP2A; IMAGE:36684.