I am new to g*power and have a question about which test I have to choose and how to interpret the given sample size.
I have 2 measurements (pre / post), one control-group and one intervention-group. In a reference study, I was able to find an effect size of .7 for the most important parameter. In g*power I chose F-test -> ANOVA RM within-between interaction, a power of 0.8 and alpha .05.
Here are my questions:
- Did I choose the correct test?
- Is the resulting sample size referring to each group or total?
- Regarding the effect size of .7 I found in a reference study, am I allowed to fill it in g*power -> effect size f, or should I leave it as it was at .25?