title: 'powerlmm': Sample size calculation LMM with 3 treatment groups
body: <p>Is it possible to use the R package 'powerlmm' to calculate the sample size for a 3x3 mixed design? It's a two level model (L1: behavioral measures; L2: individuals) with one within factor (3 levels on L1) and one between factor (3 levels on L2). Therefore we have 3 &quot;treatment&quot; groups - but powerlmm can only calculate power for 2 groups (treatment vs. control).</p>