The Wilcoxon–Mann–Whitney (WMW) test was proposed by Frank Wilcoxon in 1945 (“Wilcoxon rank sum test”) and by Henry Mann and Donald Whitney in 1947 (“Mann-Whitney U test”). However, the test is older: Gustav Deuchler introduced it in 1914. Nowadays, this test is a commonly used nonparametric test for the two-sample location problem. As with many other nonparametric tests, this is based on ranks rather than on the original observations.