Kruskal–Wallis H test
Compare three or more independent groups by their ranks.
When to use it
Use Kruskal–Wallis instead of a one-way ANOVA when you have three or more groups and the scores are ordinal or skewed.
Assumptions
Groups are independent. The outcome is at least ordinal. The test does not tell you which groups differ until you turn on post hoc.
Running it in Tensr
Options
Prop
Type
Reading the output
The three teaching methods, compared on ranks. The same moderate mean gap as the ANOVA, read without assuming a normal curve.
| Group | n | Median | Status |
|---|---|---|---|
| Lecture | 32 | 69.1 | included |
| Online | 32 | 71.05 | included |
| Workshop | 32 | 72.95 | included |
Kruskal-Wallis test of score by method (3 groups) on 96 rows. Effect size ε² = 0.076 (small; ε² < 0.01 negligible, 0.01 ≤ ε² < 0.08 small, 0.08 ≤ ε² < 0.26 medium, ε² ≥ 0.26 large). Cutoffs: Mangiafico, 2016. The primary result is significant (p = .027). This is large enough, in this sample, to treat the comparison this page is about as a real association rather than noise. Metrics: H statistic = 7.22; p-value = .027; ε² = 0.076; Effect size = small.
Reporting (APA 7)
Kruskal-Wallis test of score by method (3 groups) on 96 rows. Effect size ε² = 0.076 (small; ε² < 0.01 negligible, 0.01 ≤ ε² < 0.08 small, 0.08 ≤ ε² < 0.26 medium, ε² ≥ 0.26 large). Cutoffs: Mangiafico, 2016. This result is significant (p = .027). The effect is moderate, so report its size with the p-value.
Coming from SPSS
Analyze → Nonparametric Tests → K Independent Samples.