I am running a longitudinal experiment over 9 months. I have 2 dependent measures (water, electricity) and 5 groups (conditions, 4 experimental, 1 control). The conditions are the "between"factor, and time is the "within" factor with 9 levels (measurement points in time). I am struggling to calculate the required sample size to get 1-ß = 0.8 with alpha = 0.5. In GPower, I choose "Repeated measures MANOVA within-between interaction" as I have multiple IVs (my conditions) and I enter 5 as my number of groups. I then enter 9 as my number of measurements (as we will compare water and electricity consumption over 9 months). However, I don't know what to enter as an f(V) effect size, since I could not find any conventions for Pillais trace corrected f. Can someone help me out by clarifying what "small", "medium", and "large" conventions there are for f(V)? Previous literature reports small effect sizes, but in Cohen's ds and partial eta squares...so I am lost.