Sample size in twin studies.

Abstract

A study regarding sample size in human twin studies was conducted. The subjects were 70 studies collected from 6 journals that were psychologically oriented. Each issue of each journal, from the original publication date until the end of the year 1986, was examined in order to obtain twin studies. Data were then collected from each twin study as to total sample size, number of monozygotic and dizygotic twins, and number of male and female twins. In some studies it was not possible to determine sample sizes or data were not presented; thus, these studies were not included in the data. Descriptive statistics were used to examine the data for all journals combined. Results indicate that in the journals examined, and in the limited number of twin studies located, sample size in those twin studies appears to be low.