I have used the design_ekaterina.ods example to create my design for a similar analysis. I have two groups (Treatment, waitlist) and two sessions (pre and post intervention) and I am mainly interested in the interaction effect. My question is should I only use the two contrasts defined in the example or should I also look at the t2>t1, and the interaction of t2>t1, G2>G1. Is this contrast somehow similar to the other one or not. I am a bit confused on that.

I do not want run too many analysis that decreases my analysis power but I also do not want to miss potential significant results.

Also, I was wondering if you could introduce a paper that explains the F-test and G-stats in more details.

Thanks,

Sara