Table 1.

Detection of the phenotype to environment transmission in the ACE simplex and in the AE simplex

αk	βk	χ2	~N
ACE	(parameter set 1)
.10	.10	2.096	11,700
.10	.15	5.034	4,700
.15	.10	1.976	12,100
.15	.15	4.885	4,800
−.10	.10	2.487	9,600
.10	−.10	5.334	4,500
−.10	−.10	3.670	6,500
ACE	(parameter set 2)
.10	.10	1.234	19,300
.10	.15	2.588	9,250
.15	.10	1.283	18,650
.15	.15	2.735	8,750
−.10	.10	0.907	26,350
.10	−.10	6.649	3,600
−.10	−.10	3.892	6,100
AE	(parameter set 3)
.10	.10	38.408	620
.10	.15	89.690	260
.15	.10	41.679	580
.15	.15	97.266	240
−.10	.10	27.754	860
.10	−.10	27.756	860
−.10	−.10	21.653	1,100

The χ² equals the non-centrality parameter times N (N = NMZ (1000) + NDZ (1000)) obtained by fitting the model with the Ph->E transmission parameters (α₁, α ₂ = α₃, β₁, β₂ = β₃) fixed to zero. The approximate sample size (~N) required is based on a power calculation given the type I error probability of alpha = 0.05 and df = 4, and an equal number of MZ and DZ twin pairs (N = Nmz + Ndz)