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. Author manuscript; available in PMC: 2013 Dec 5.
Published in final edited form as: J Educ Psychol. 2011 Oct 15;104(3):10.1037/a0027646. doi: 10.1037/a0027646

Table 3. Intraclass twin correlations and proportion of variance due to A, C, E (95% CI in parentheses).

Mathl Math2 Math3 WD1 WD2 RC1 RC2
Twin correlations
MZ .62
(.59, .65)		 .55
(.52, .59)		 .57
(.53, .60)		 .77
(.74, .79)		 .72
(.70, .74)		 .46
(.42, .50)		 .56
(.52, .59)
 n pairs 1627 1627 1627 1511 1702 1715 1748
DZ .39
(.36, .42)		 .35
(.32, .38)		 .32
(.29, .36)		 .39
(.36, .42)		 .41
(.38, .44)		 .30
(.27, .33)		 .37
(.33, .40)
 n pairs 2902 2902 2902 2603 2978 3057 3117
Proportion of variance due to A, C, E
a2 .47
(.38, .53)		 .42
(.34, .49)		 .50
(.42, .56)		 .74
(.68, .76)		 .64
(.59, .70)		 .34
(.27, .42)		 .37
(.30, .44)
c2 .16
(.10, .23)		 .15
(.08, .21)		 .08
(.03, .14)		 .02
(.01, .08)		 .08
(.03, .13)		 .13
(.04, .19)		 .18
(.13, .24)
e2 .37
(.35,.40)		 .44
(.41, .47)		 .42
(.40, .45)		 .24
(.22, .25)		 .28
(.26, .30)		 .53
(.50, .56)		 .45
(.42, .47)

Note: Mathl = Understanding Number; Math2 = Non-Numerical Processes; Math3 = Computation and Knowledge; WD1 = TOWRE; WD2 = WJ-III Reading Fluency; RC1 = PIATrc; RC2 = GOAL.