Table 6.

Power of S_pairs and S_ad in the Absence of Parental Genotypes^[Note]

	Power
Model, Penetrances for Genotypes, KS (%),and Markera	Spairs	Sad(one)	Sad(all)
Recessive (q = .316):
DD = .12, Dd = .12, dd = .40, KS = 16.7:
M1	.369	.386	.453
M2	.300	.272	.337
DD = .13, Dd = .13, dd = .33, KS = 15.9:
M1	.099	.103	.098
M2	.076	.073	.076
Dominant (q = .0513):
DD = .12, Dd = .40, dd = .40, KS = 17.3:
M1	.313	.371	.439
M2	.249	.276	.308
DD = .13, Dd = .33, dd = .33, KS = 16.2:
M1	.106	.106	.116
M2	.086	.085	.097
Additive (q = .1):
DD = .12, Dd = .26, dd = .40 KS = 16.1:
M1	.097	.103	.126
M2	.080	.066	.087
DD = .13, Dd = .23, dd = .33, KS = 15.6:
M1	.037	.046	.038
M2	.034	.035	.029

Note.— Power of S_pairs and S_ad under six different models, without TRD effects, for 400 ascertained sibships of various sizes. Two genotyping scenarios are considered: typing one unaffected sibling or all unaffected siblings. Parental genotypes are unavailable. Power is estimated at markers M₁ and M₂ from 1,000 simulated replicates, for a nominal level of 1%.

^aPenetrances are given in terms of the genotypes at the disease locus, where d is the susceptibility allele, with frequency q. K_S is the sibling recurrence risk for the disease model. In all cases, the disease prevalence is 15%.