What Kruskal-Wallis and Mann-Whitney actually run on
Fifteen toy fragment lengths (mm) from three schools. Neither test ever looks at these raw numbers. Both convert them to ranks first. Watch what that conversion does.
Plotted at their true position on the number line
Once every point has a rank, Kruskal-Wallis only needs each group's rank total
| School | n | Rank sum R | R² / n |
|---|