Repeated-measures ANOVA
Compare three or more measurements from the same people.
When to use it
Use repeated-measures ANOVA when the same people contribute every score and you have three or more conditions in separate columns. For example: does a mood rating change across week 1, week 2, and week 3?
Two columns only: the paired-samples t-test is the simpler test. A between-subjects factor as well as the repeated one is mixed ANOVA.
Assumptions
The differences between each pair of conditions should have similar spread. That is sphericity. Tensr runs Mauchly’s test. If Mauchly’s p is below .05, the report says sphericity may be violated and adds Greenhouse–Geisser and Huynh–Feldt corrections.
Tensr does not run Shapiro–Wilk on the differences. If the scores are ranks or badly skewed, use the Friedman test.
Partial η² is computed for the within-subjects effect. You do not choose it in the dialog.
Running it in Tensr
Options
Prop
Type
Reading the output
Thirty-six people across three weeks. Later weeks were built a little higher, with enough noise that the weeks still overlap.
| Source | F | df (num) | df (den) | p-value |
|---|---|---|---|---|
| condition | 8.278 | 2 | 70 | < .001 |
| Condition | n | Mean | SD |
|---|---|---|---|
| week1 | 36 | 19.906 | 5.479 |
| week2 | 36 | 20.889 | 4.685 |
| week3 | 36 | 23.953 | 4.962 |
Repeated measures ANOVA on 3 conditions, 36 subjects. Repeated measures ANOVA on 3 conditions, 36 subjects. Metrics: Subjects = 36; Partial η² = 0.191.
Reporting (APA 7)
Repeated measures ANOVA on 3 conditions, 36 subjects. Report the estimate in the table. This procedure is not summarised by one p-value.
Coming from SPSS
Analyze → General Linear Model → Repeated Measures.
SPSS prints tests of within-subjects effects with sphericity assumed, Greenhouse–Geisser, Huynh–Feldt, and lower bound in one table, plus optional pairwise comparisons. Tensr splits the uncorrected test, Mauchly’s test, and the two corrections into three tables, and does not run pairwise tests.
Related
The rank alternative is the Friedman test. Two measurements: paired-samples t-test. A grouping factor as well: mixed ANOVA.