I need to calculate effect size for a mixed ANOVA design. I need it because I'm using GPower3 to calculate a rough sample size for a full study. I have pilot data. Based on this page:
and the GPower3 software, it looks like there are 3 ways to calculate an effect size:
- use variances
- use group means
Is there any rational for picking one over another? Since I have the pilot data, I guess I was just going to use the variances to calculate the effect size. The formula I have for that is:
f (effect size) = sqrt(Variance Explained / Variance Error)
Based on the summation rule:
Total Variance = Variance Explained + Variance Error
Is this correct?
If I have unequal group sizes, could I use the pooled variance formula for the Variance Error term?
I also noticed that this effect size formula using the variances is quite similar to the F statistic:
F = Variance Explained / Variance Error
Is this correct and/or is there a relationship between them?
Thanks in advance.