Sample size
We anticipated having approximately 160 clusters, with an average of 350 beds per cluster. In a 2 × 2 factorial design assuming no interaction and similar effects for each factor, a test of each intervention at 6 months in an ANCOVA design would achieve 90% power to detect an absolute mean difference of 0.3 in the primary outcome (i.e., a difference in the mean number of CNS-active medications per month of 3 versus 2.7). Based on previous data, we assumed a standard deviation of 4, an intracluster correlation coefficient of 0.05, a cluster autocorrelation of 0.8, and an individual autocorrelation of 0.9 [