Repeated Measures ANOVA SPSS

SPSS repeated measures ANOVA tests if the means of 3 or more metric variables are all equal in some population. 
The simplest repeated measures ANOVA involves 3 outcome variables, all measured on 1 group of cases (often people). Whatever distinguishes these variables (sometimes just the time of measurement) is the within-subjects factor.

 

SPSS

Analyze - General Linear Model - Repeated Measuers

 

1. We may freely choose a name for our within-subjects factor. 

2. We may also choose a name for our measure: whatever each of the four variables is supposed to reflect. 

3. We now select all four variables and move them to the Within-subjects variables box with the arrow to the right.

4. Under Options we'll select Descriptive statistics.

5. Clicking Paste results in the syntax below.

 

Repeated Measures ANOVA Output - Mauchly’s Test

We now turn to Mauchly's test for the sphericity assumption. As a rule of thumb, sphericity is assumed if Sig. > 0.05. 

Repeated Measures ANOVA Output - Within-Subjects Effects

Since our data seem spherical, we'll ignore the Greenhouse-Geisser, Huynh-Feldt and lower bound results in the table below. We'll simply interpret the uncorrected results denoted as “Sphericity Assumed”.

 

 

Reporting the Measures ANOVA Result

When reporting a basic repeated-measures ANOVA, we usually report

• the descriptive statistics table
• the outcome of Mauchly's test and
• the outcome of the within-subjects tests.