Mann-Whitney U Test Calculator
Compare two independent groups using ranks.
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Enter data for each group, comma-separated. The calculator ranks all observations together, computes the U statistic, and approximates the p-value using the normal approximation. This test does not assume normal distributions.
About This Calculator
The Mann-Whitney U test (also called Wilcoxon rank-sum test) is a non-parametric test for comparing two independent groups. It tests whether one group tends to have larger values than the other. Unlike the t-test, it does not assume normality and works with ordinal data or non-normal distributions.
Frequently Asked Questions
When should I use Mann-Whitney instead of a t-test?
Use it when your data is ordinal, clearly non-normal, or has small sample sizes where normality cannot be verified. For normal data, the t-test has more power.
What does the U statistic represent?
U counts the number of times a value in one group precedes a value in the other group when all values are ranked. A very small or very large U indicates group differences.
Is this the same as the Wilcoxon rank-sum test?
Yes. The Mann-Whitney U test and Wilcoxon rank-sum test are equivalent tests with different formulations but the same p-value.