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 |
|---|