| Title:The name assigned to the document by the author. This field may also contain sub-titles, series names, and report numbers. | Are Apparent Sex Differences in Mean IQ Scores Created in Part by Sample Restriction and Increased Male Variance? |
| Authors:Personal author, compiler, or editor name(s); click on any author to run a new search on that name. | Dykiert, Dominika; Gale, Catharine R.; Deary, Ian J. |
| Descriptors:Terms from the Thesaurus of ERIC Descriptors; used to tag materials by subject to aid information search and retrieval. Click on a Descriptor to initiate any new search using that term. | Psychological Testing; Cognitive Tests; Intelligence Quotient; Factor Analysis; Longitudinal Studies; Gender Differences; Males; Cognitive Ability; Foreign Countries; Scores; Computation; Age Differences; Sampling |
| Source:The entity from which ERIC acquires the content, including journal, organization, and conference names, or by means of online submission from the author. | Intelligence, v37 n1 p42-47 Jan-Feb 2009 |
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| Abstract:A brief narrative description of the journal article, document, or resource. | This study investigated the possibility that apparent sex differences in IQ are at least partly created by the degree of sample restriction from the baseline population. We used a nationally representative sample, the 1970 British Cohort Study. Sample sizes varied from 6518 to 11,389 between data-collection sweeps. Principal components analysis of scores obtained on four cognitive tests administered at age 10 was used to obtain estimates that we name "IQ". These age-10 scores were then used to estimate the sex differences at age 10, and also among participants in the two later waves, at age 26 and 30. At age 10, there was a small but significant advantage for boys (Cohen's d = 0.081). Boys had greater variability in these IQ scores. We then investigated how this very small male advantage at 10 changed with sample restriction. We used the same IQs obtained at age 10, but considered only those subjects who returned for data-collection sweeps at ages 26 and 30 years. Subjects returning at age 26 and 30 were more likely to be females and to have higher age-10 IQ scores. Attrition at age 30 was 28% and the male advantage in IQ scores increased by 15%. Attrition at age 26 was 43% and the male advantage in IQ scores increased by 48%. The findings underline the importance of monitoring attrition in longitudinal studies, as well as emphasising the need for representative samples in studying sex differences in intelligence. A proportion of the apparent male advantage in general cognitive ability that has been reported by some researchers might be attributable to the combination of greater male variance in general cognitive ability and sample restriction, though this remains to be tested in a sample with an appropriate mental test battery. (Contains 1 figure and 1 table.) |