. 2008 Apr 4;38(4):372–389. doi: 10.1007/s10519-008-9201-8

Table 5.

Number of sib pairs required to detect main effects of QTL and environment, and G × E interaction effects of different effect sizes, in the context of different allele frequencies, and different types of environments (categorical versus continuous) for power of .80 with α = .05 when all other effects are 0

Effect size		Zero effects freely estimated			Zero effects fixed to zero
		Environment			Environment
		b ₁ = .2	b ₁ = .5	Continuous	b ₁ = .2	b ₁ = .5	Continuous
Main effect QTL^a
1%	p = .2	3,607	1,441	737	600	600	600
2.5%		1,400	561	288	235	235	235
5%		664	266	142	116	116	116
1%	p = .5	2,290	921	473	385	385	385
2.5%		890	359	185	151	151	151
5%		422	171	92	75	75	75
Main effect environment^b
1%	p = .2	3,864	2,468	2,581	600	384	386
2.5%		1,509	964	1,010	228	146	152
5%		716	458	490	110	71	75
1%	p = .5	1,157	743	770	600	384	386
2.5%		452	291	302	228	146	152
5%		216	139	147	110	71	75
Interaction^a
1%	p = .2	1,111	710	725	149	186	278
2.5%		415	266	289	57	70	111
5%		186	120	142	27	33	55
1%	p = .5	706	454	463	117	296	378
2.5%		265	171	186	44	70	151
5%		119	77	92	21	33	75

^aThese power calculations assume 2 degrees of freedom

^bThese power calculations assume 1 degree of freedom