I would like to report the power observed with my mixed model analysis (or repeated measures ANOVA). My experiment followed a completely within subject design with 2 independent factors (two levels & 5 levels, respectively). 12 participants were recruited to run the 10 combos (5x2) twice (repeated observations), yielding 240 observations. There were some missing data, so the actual total observations was 230.
I have never used G*Power before but it seems like a pretty powerful tool. I attempted to run a post-hoc analysis as shown below. The resulting power is so high (0.933) that I'm a little skeptical. I've taken the sample size to mean # of subjects (12) and that the number of groups refers to levels for between-subject factors, which I have none. The corr among rep measures was just something I estimated [edit: I thought this parameter isn't making a big difference, but it is. Changing it to 0.5 actually lowers the power to 0.5]
Did I enter anything wrong? I would appreciate it if anyone could help me figure out this power analysis.
Analysis: Post hoc: Compute achieved power Input: Effect size f = 0.2 α err prob = 0.05 Total sample size = 12 Number of groups = 1 Number of measurements = 10 Corr among rep measures = 0.8 Nonsphericity correction ε = 1 Output: Noncentrality parameter λ = 24.0000000 Critical F = 1.9758061 Numerator df = 9.0000000 Denominator df = 99.0000000 Power (1-β err prob) = 0.9333319