Table 2.

Combinations of enrollment sites (cluster) and subjects per site

Clusters	Events per cluster	Total events	Patients per cluster	Patients per cluster+15% attrition	Power
30	15	300	48	55	0.84
20	20	400	63	72	0.804
25	20	500	63	72	0.876
30	20	600	63	72	0.906
15	25	375	79	91	0.809
20	25	200	79	91	0.842
25	25	625	79	91	0.927
15	30	450	95	109	0.857
10	35	350	111	128	0.818
15	35	525	111	128	0.916
10	40	400	126	145	0.836