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

Published in final edited form as: Learn Individ Differ. 2010 Oct 1;20(5):549–553. doi: 10.1016/j.lindif.2010.06.005

Table 2.

Twin intra-class correlations

CHAOS	MZ	N	DZ	N	Total N
9 year	0.65 (0.62 – 0.67)	1112	0.52 (0.48 – 0.55)	1878	2990
12 year	0.64 (0.61 – 0.66)	1935	0.56 (0.53 – 0.58)	3449	5384

^†9–12 year	0.75 (0.72 – 0.77)	877	0.62 (0.59 – 0.65)	1460	^*2337

MZ = monozygotic twins; N = number of complete twin pairs; DZ = dizygotic twins; 95% confidence intervals shown in parentheses

^†

First principle component composite of CHAOS at age 9 and 12

2337 complete twin pairs (out of the 4956 individuals with data at both ages who were all included in the more comprehensive structural equation modelling analyses).