ASSESSMENT: Global Sex Differences in Test Score Variability

[FarCenter]

http://www.sciencemag.org/cgi/content/full/322/5906/1331

Do boys and girls differ in their intellectual and cognitive abilities and, if so, in what way? These questions have raised considerable debate, both in terms of average performance and in terms of variability around the average.

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Implications and Conclusions

Our analysis of international test score data shows a higher variance in boys' than girls' results on mathematics and reading tests in most OECD countries. How this translates into educational achievement is a matter open for discussion. Higher variability among boys is a salient feature of reading and mathematics test performance across the world. In almost all comparisons, the age 15 boy-girl variance difference in test scores is present. This difference in variance is higher in countries that have higher levels of test score performance.

Sex differences in means are easier to characterize: It is evident from the PISA data that boys do better in mathematics, and girls do better in reading. This has a compositional effect on the variance differences as well. The higher boy-girl variance ratio in mathematics comes about because of an increased prevalence of boys in the upper part of the distribution, but the higher variance in reading is due to a greater preponderance of boys in the bottom part of the test score distribution. Because literacy and numeracy skills have been shown to be important determinants of later success in life (for instance, in terms of earning higher wages or getting better jobs), these differing variances have important economic and social implications (22).

We therefore confirm that 15-year-old boys do show more variability than girls in educational performance, with specifics that differ according to whether mathematics or reading are being studied and tested. These results imply that gender differences in the variance of test scores are an international phenomenon and that they emerge in different institutional settings.