. Author manuscript; available in PMC: 2007 Sep 19.

Published in final edited form as: Health Psychol. 2007 Sep;26(5):610–617. doi: 10.1037/0278-6133.26.5.610

Table 2.

Twin correlations and number of respondent twin pairs by sex and zygosity

Variable	MZF	DZF	MZM	DZM	DZO
Age¹	.671	.392	.625	.252	.292
N Partners²	.483	.282	.552	.254	.279
Initiation²	.864	.613	.907	.564	.384
N twin pairs	472	414	313	387	862

Note: Age = Age at first sexual intercourse. N Partners = Number of sexual partners excluding abstainers. Initiation = dichotomous scoring of initiation or abstinence (zero versus one or more partners). Superscripts indicate the type of correlation computed:

Pearson Product Moment Correlation;

Polychoric Correlation.