. Author manuscript; available in PMC: 2015 Nov 7.

Published in final edited form as: J Child Psychol Psychiatry. 2014 Mar 10;55(9):1056–1064. doi: 10.1111/jcpp.12224

Table 1.

Descriptive statistics, phenotypic correlations, and twin intra-class correlations of the study variables.

Variables	Phenotypic Correlations				Twin Intra-class correlations
Variables	MA	GA	MPS	RC	MZ	DZ
Mathematical Anxiety	1				.46^*	.11
General Anxiety	.37^*	1			.43^*	.21^*
Math Problem Solving	−.32^*	−.10	1		.75^*	.55^*
Reading Comprehension	−.17^*	.00	.58^*	1	.77^*	.32^*

	Descriptive Statistics

M	48.77	11.42	43.44	45.65
SD	16.44	2.78	6.33	7.64
Skewness	.92	.61	−.17	−.41
Kurtosis	.95	.42	.34	−.00
Min	14.00	6.00	22.00	21.00
Max	126.00	21.00	62.00	62.00
Possible Range	14–130	4–24	0–63	0–68
N	506	391	509	491

Note: MA = mathematical anxiety; GA = general anxiety; MPS = math problem solving; RC = reading comprehension. The differences between N for MA, math problem solving, and reading comprehension are due to normal variation in N (test times, fatigue, etc). The N for general anxiety questionnaire is lower because that was part of a packet of questionnaires given as a take-home between visits. In contrast, the MA questionnaire was administered at the time of the second home visits.

p < .05.