Table 6.

Comparison of sample sizes given differences in expected odds ratio, power and ratio between cases and controls

Case–control ratio	OR	n.total	n.case	n.control	n.total	n.case	n.control	n.total	n.case	n.control
		Power = 0.9			Power = 0.8			Power = 0.7
2	1.5	2,922	974	1,948	2,169	723	1,446	1,698	566	1,132
	2	891	297	594	663	221	442	519	173	346
	2.5	468	156	312	348	116	232	273	91	182
	3	303	101	202	228	76	152	180	60	120
	3.5	219	73	146	165	55	110	132	44	88
	4	171	57	114	129	43	86	102	34	68
	4.5	138	46	92	105	35	70	84	28	56
	5	117	39	78	90	30	60	72	24	48
2	5				90	30	60
3	5				104	26	78
4	5				120	24	96
5	5				132	22	110
6	5				147	21	126
7	5				168	21	147
8	5				180	20	160
9	5				200	20	180
10	5				209	19	190
5	1.5				3,300	550	2,750
	2				996	166	830
	2.5				522	87	435
	3				336	56	280
	3.5				246	41	205
	4				192	32	160
	4.5				156	26	130
	5				132	22	110

OR: Odds ratio; n.total: total sample size; n. case: number of cases; n control: number of controls.