HOME
PAGE

HIGHIQWORLD FAQ AND HELP

HIGHIQWORLD APPLICATIONS

IQ AND OTHER TESTS

You are not logged in. Access is limited. Login or see membership information. • HighIQWorld

Education, Intelligence, and IQ

Blog Entry

Are Apparent Sex Differences in Mean IQ Scores Created in Part by Sample Restriction and Increased M

posted by Karyn Peters, Group AdministratorSaturday, January 30th 2010 @ 3:19 PM (not yet rated) post viewed 142 times

Title:	Are Apparent Sex Differences in Mean IQ Scores Created in Part by Sample Restriction and Increased Male Variance?
Authors:	Dykiert, Dominika; Gale, Catharine R.; Deary, Ian J.
Descriptors:	Psychological Testing; Cognitive Tests; Intelligence Quotient; Factor Analysis; Longitudinal Studies; Gender Differences; Males; Cognitive Ability; Foreign Countries; Scores; Computation; Age Differences; Sampling
Source:	Intelligence, v37 n1 p42-47 Jan-Feb 2009





Abstract:	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.)

rate this post:

Comments

Karyn Peters
Group Administrator

iquadrivium said on Monday, February 1st 2010 @ 6:50 PM:

Registered users may comment on and/or Retweet any blog post or article.