Kruskal–Wallis Exact Ties
Inspect tied ranks and compare a small exact allocation test with its asymptotic reference.
Free theory articleInspect tied ranks and compare a small exact allocation test with its asymptotic reference.
Concept & interpretation
The Kruskal–Wallis test is a non-parametric method used for comparing two or more independent samples of equal or different sample sizes. It extends the Mann-Whitney U test, which is used for comparing only two groups. When observations have identical values, they receive averaged ranks. This tie-correction scales the final test statistic H, which affects the exact permutation test probability distribution.
Interactive Experiment
You can interact with the Kruskal–Wallis Exact Ties module to see how ties and group configurations affect the test statistic and exact permutation probabilities.
- Select the Data control and set it to Separated to observe the behavior when there are no ties (C = 1.0).
- Change the Data control to Tied to observe the tie correction take effect, increasing the final H and altering the permutation reference.
- Change the Group probe control to view the specific Selected mean rank for each individual group without changing the global H statistic.