Evaluation of a system of structured, pro-active care for chronic depression in primary care: a randomised controlled trial

Table 2 Four Point Difference in BDI

ICC	Design effect*	Total sample size		Number of practices required
		Required	With 25% drop-out
0	1	400	534	40
0.01	1.09	436	581	44
0.02	1.18	472	630	47
0.03	1.27	508	678	51
0.04	1.36	544	725	54
0.05	1.45	580	774	58

*Design effect = 1 + (n-1) × ICC, based on clusters with 10 individuals per cluster.

ISSN: 1471-244X