Fig. 6

Power curves for a binary outcome assuming 25 clusters, each with 20 subjects and 6 time points at which measurements are taken (including one baseline time). We varied the way in which the assumed linear time effect is included in the model (if at all). Panel (a) shows the results for a repeated cohort design; panel (b) shows the results for the closed cohort design, assuming a cluster-level ICC of 0.1 and varying the participant-level ICC; panel (c) shows the results for the closed cohort design, assuming a cluster-level ICC of 0.5 and varying the participant-level ICC