Hello everyone, This is my first post here. I need icc for power calculation. I have outcome variables test scores and student's effort to study .Can you hint me any source to assume icc ? I have been told to look at similar study so I was checking data of a similar study. I am trying to find out the intraclass correlation between testscores and then student's effort separately, not between them. I have the test score, student ids and they are clustered by village id.I also have 2 treatment groups and 1 control. I have tried the stata command but I can't understand who is my rater/target? Not sure whether to pick one way or two way.It is a Randomised Controlled Trial model.for power calculation I should be using : power twomeans 0, cluster k1(75) k2(75) m1(15) m2(15) power(.8 .9) rho() I need to assume icc/rho.Thanks.