Table 2.

Sample size requirements for 80% power in EWAS twin and case-control designs

Diff	Twin				Case-control
	P < 0.05		P < 1 × 10−6		P < 0.05		P < 1 × 10−6
	t-testa	Wilcoxb	t-testa	Wilcoxb	t-testc	Wilcoxd	t-testc	Wilcoxd
7%	30	30	178	178	37	37	211	211
8%	25	25	145	149	30	30	169	169
9%	20	20	117	117	24	24	137	137
10%	17	18	98	102	20	21	112	110
11%	15	15	81	83	17	18	96	95
12%	13	13	71	71	15	16	80	80
13%	11	12	63	69	13	13	70	70
14%	10	11	55	62	11	13	61	63
15%	9	10	50	57	10	11	54	57

Diff, mean methylation difference between affected and unaffected individuals.

^at test, paired t test.

^bWilcox, Wilcoxon signed-rank test.

^ct test, two-sample t test.

^dWilcox, Wilcoxon rank-sum test.