. Author manuscript; available in PMC: 2011 May 1.

Published in final edited form as: Behav Genet. 2009 Nov 21;40(3):327–337. doi: 10.1007/s10519-009-9316-6

Table 3.

Fit statistics for bivariate models of observed and parent-rated inhibitory control, and variance estimates and genetic and environmental correlations for the best-fitting bivariate model of observed and parent-rated inhibitory control (95% CI)

Fit statistics for bivariate models
	Overall fit of model				Relative fit of model^a
	χ ²	df	p	AIC	χ ^2diff	df^diff	p
1. ACE Observed/ACE Parent-rated	11.02	11	.44	−10.98	–	–	–
2. AE Observed/ACE Parent-rated	11.06	13	.61	−14.94	.04	2	.98
3. Model 2 plus No A Covariance	32.09	14	.00	4.09	21.07	3	.00
4. Model 2 plus No E Covariance	11.13	14	.68	−16.87	.11	3	.99

Variance estimates and genetic and environmental correlations (best-fitting model)
	Variance estimates			Genetic and environmental correlations
	h²	c²	e²	r_g	r_c	r_e
Observed IC	.39 (.25–.51)	–	.61 (.49–.75)
Parent-rated IC	.58 (.39–.80)	.27 (.05–.44)	.15 (.12–.20)
Observed IC-Parent-rated IC				.47 (.28–.68)	–	–

Note: χ² Chi-square fit statistic; df degrees of freedom; AIC Akaike’s Information Criterion (AIC is used to compare the relative fit of models, those with a lower AIC are judged to fit better); χ^2diff Chi-square difference between full ACE/ACE model and reduced model; df^diff df difference between full ACE/ACE model and reduced model; A additive genetic effects; C shared environmental effects; E nonshared environmental effects; h² heritability; c² shared environmental variance; e² nonshared environmental variance; r_g genetic correlation; r_c shared environmental correlation; r_e nonshared environmental correlation. Boldface denotes best fitting model. Shared and nonshared environmental correlations were not included in the best-fitting model

Relative fit of the model determined by the χ^2diff between full ACE model and reduced model