# Permutation test and the Mann-Whitney U test

Source: https://onco.cc/terms/permutation-test/  
OnCo record `permutation-test` (Term). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

A permutation test builds the null distribution by shuffling labels (or spot positions) many times and asks how often chance does as well as the real result; the Mann-Whitney U test compares two groups by ranks without assuming a normal distribution.

## Summary

A permutation test is an exact hypothesis test in which the null distribution of the statistic is obtained by recomputing it over rearrangements of the labels (Wikipedia). It gives p-values for Moran's I, for enrichment scores and for any model metric where the parametric distribution is unknown. The Mann-Whitney U test is the non-parametric test that randomly chosen values from two populations have the same distribution (Wikipedia), the default for comparing, say, predicted risk between responders and non-responders.

## Fields

- Kind: Term
- Last checked: 2026-09-24
- Also known as: permutation test; permutation p-value; label shuffling; shuffled labels; Mann-Whitney U test; Mann-Whitney test; Wilcoxon rank-sum test; rank-sum test; non-parametric test
- Tags: cansim-terms

## Notes

- Listed in the CanSim terms map 1.0.0 (docs/onco/terms.json, generated 2026-09-24), CC BY 4.0, attribution: CanSim project, an open, public-data-first cancer foundation-model programme; CanSim page path /terms/permutation-test.

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/Permutation_test
- Wikipedia: Mann-Whitney U test: https://en.wikipedia.org/wiki/Mann%E2%80%93Whitney_U_test
- Wikipedia: https://en.wikipedia.org/wiki/Permutation_test

## Connected records

- terms: [Bootstrap resampling](https://onco.cc/terms/bootstrap/), [Cancer AI vocabulary (CanSim terms map)](https://onco.cc/terms/cancer-ai-vocabulary/), [Spatial autocorrelation (Moran's I)](https://onco.cc/terms/spatial-autocorrelation/), [Spearman rank correlation](https://onco.cc/terms/spearman-correlation/)

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