APA Dictionary of Psychology

a nonparametric test of centrality for ordinal data that contrasts scores from two independent samples to assess whether there are significant differences between the two sets of rankings. The statistic obtained from this test, U, is calculated by summing the number of ranks in one group that are smaller than each of the ranks in the other group. A Mann–Whitney U test is analogous to a one-way analysis of variance, except that the former is conducted with ranked data and the latter is conducted with continuous data. See also Wilcoxon–Mann–Whitney test. [Henry Berthold Mann (1905–2000), Austrian-born U.S. mathematician; Donald Ransom Whitney (1915–2001), U.S. statistician]