# One-way repeated measures ANOVA with G*Power

I have made an experiment with 28 subjects. All made the experiments under 3 different conditions (A, B and C). So I have a table like this:

No. A B C
1   3 6 4
2   6 2 6
...


Now I just want to perform a RM-ANOVA or a Friedman test or a Quade test. That's not the problem.

I want to use GPower to determine the necessary alpha value to detect e. g. a "medium" effect. I do not get how to use GPower in this case.

Here is a screenshot of how I do it for a t-test: Now I want to do the same for more than 2 conditions. Can somebody point out how to do that? Here's a screenshot of the possibilities: EDIT: I looked it up, and apparently it is called One-way repeated measures ANOVA. So how can I to One-way repeated measures ANOVA with G*Power to determine the required alpha value (given effect size and so on)?

## 1 Answer

I think I found it here:

Link to book chapter, additional material

Applied to my problem I guess it will be like this: F tests - ANOVA: Repeated measures, within factors
Analysis:   Criterion: Compute required α
Input:  Effect size f   =   0.25
Power (1-β err prob)    =   0.80
Total sample size   =   28
Number of groups    =   1
Number of measurements  =   3
Corr among rep measures =   0.3
Nonsphericity correction ε  =   1
Output: Noncentrality parameter λ   =   7.5000000
Critical F  =   2.2129741
Numerator df    =   2.0000000
Denominator df  =   54.0000000
α err prob  =   0.1191999