Mixed ANOVA
Test one between-subjects factor and one repeated-measures factor together.
When to use it
Use mixed ANOVA when some groups are separate people and another factor is the same people measured more than once. For example: do control and treatment groups differ in how their scores change from pre to post?
The interaction is usually the result you care about. It asks whether the pre-to-post change is different in the two groups.
Assumptions
Between groups, the spread of scores should be similar. Within people, sphericity applies when there are three or more repeated measurements. With only two repeated measurements, sphericity holds automatically, and Mauchly’s test is not informative.
With only two repeated columns, Tensr does not print Mauchly’s test. It does not run Levene’s test or Shapiro–Wilk. Partial η² is printed for each effect. You do not choose it.
Running it in Tensr
Options
Prop
Type
Reading the output
Twenty-four people in control and 24 in treatment, each with a pre and a post score. Treatment was built to gain a bit more than control. The gains overlap.
| Source | SS | df | MS | F | p | partial η² |
|---|---|---|---|---|---|---|
| Between: group | 2.22 | 1 | 2.22 | 0.02 | .889 | 0.0004258 |
| Error | 5213 | 46 | 113.321 | — | — | — |
| Source | SS | df | F | p | partial η² |
|---|---|---|---|---|---|
| condition | 175.5 | 1 | 9.947 | .003 | 0.178 |
| group × condition | 48.167 | 1 | 2.73 | .105 | 0.056 |
The group main effect is not significant, F = 0.02, p = .889. Scores change from pre to post, F = 9.947, p = .003. The extra treatment gain, the group × condition interaction, is not significant, F = 2.73, p = .105.
Reporting (APA 7)
A mixed ANOVA (n = 24 per group) found no group effect, F = 0.02, p = .889, a pre-to-post change, F = 9.947, p = .003, and no group × condition interaction, F = 2.73, p = .105.
Coming from SPSS
Analyze → General Linear Model → Repeated Measures, with a between-subjects factor.
SPSS prints the interaction F, its degrees of freedom, and partial η² in the within-subjects table.
Related
No between-subjects factor: repeated-measures ANOVA. No repeated factor: one-way ANOVA or the independent-samples t-test. The rank alternative for the repeated factor alone is the Friedman test. Tensr does not offer a nonparametric mixed ANOVA.