. 2000 Mar 8;66(3):1119–1131. doi: 10.1086/302808

Table 2.

Efficiency of the Prospective and Retrospective for Estimating the Absolute Penetrance in Carriers, Relative to the Joint Likelihood^[Note]

	var₀/var^a
	Genetic Odds Ratio = 20			Genetic Odds Ratio = 2
	Sibship Size			Sibship Size
Model and Likelihood	2	3	4	2	3	4
	q = .14			q = .44
Recessive model:
Prospective	NA^b	.83	.91	NA^b	.95	.96
Retrospective	1.00	.51	.49	1.00	.016	.016
	q = .02			q = .19
Additive model:
Prospective	NA^b	.96	.98	NA^b	.99	.98
Retrospective	1.00	.11	.12	1.00	.003	.003
	q = .01			q = .10
Dominant model:
Prospective	NA^b	.90	.97	NA^b	.98	.98
Retrospective	1.00	.24	.22	1.00	.010	.010

Note.—The population disease rate was fixed at 10%, and allele frequencies were chosen so as to fix the proportion of cases caused by the genetic factor.

var = the asymptotic variance of the maximum-likelihood estimate for the log genetic odds ratio for the prospective, retrospective, or joint likelihood. var₀ = the asymptotic variance of the maximum-likelihood estimate for log genetic odds ratio for the standard conditional likelihood.

For sibships of size two, the prospective likelihood is identical to the standard conditional likelihood, and hence cannot estimate absolute penetrances.