Table 1.

Estimates of the Minimum Detectable Difference (MDD) for trial with 20 clusters per arm, to detect an increase in an event rate from 40%

	Power = 80%		Power = 90%
	40% vs 50%	MDD	40% vs 50%	MDD
ICC = 0.005	nI = 385	N/A	nI = 515	N/A
	nC = 440		nC = 600
	m = 22		m = 30
ICC = 0.07		MDD = 12%		MDD = 14%
		nI = 267		nI = 262
		nC = 3,780		nC = 2,920
		m = 189		m = 146