📉 Mann-Whitney U Test Calculator
Compare two independent samples without assuming a normal distribution. Enter values for Group A and Group B to run a Mann-Whitney U test.
What the Mann-Whitney U test does
The Mann-Whitney U test (also called the Wilcoxon rank-sum test) checks whether two independent groups come from the same distribution, without assuming the data is normally distributed. It works by ranking every value from both groups together and comparing the sum of ranks in each group.
How this calculator works
Enter the values for Group A and Group B (leave extra slots at their default or clear them if you have fewer than five values per group). The calculator combines and ranks all values, handling tied values by averaging their ranks, then computes the U statistic for each group and reports the smaller one. For reasonably sized samples, it also converts U into a z-score and an approximate two-tailed p-value using the normal approximation.
The normal approximation used here is most accurate when each group has at least 8-10 observations; for very small samples, exact Mann-Whitney tables give a more precise p-value. This tool is for general educational and planning purposes.