Sibling data may be used as a covariant statistically controlling family background for testing the adequacy of age-standardized scores; for testing the interval scale of mental measurements; for analyzing correlations into between- and within-family components; and for detecting cultural sources of variance. (Author/GDC)

An analysis of intelligence quotient (IQ) in relation to head size was performed on about 14,000 children aged 4 and 7 years, almost equally divided by race (white and black) and sex. Correlation between head size (by inference, brain size), and IQ is established as a within-families correlation. (SLD)

The contribution of heredity to scores on a digit span intelligence test, Jensen's Memory for Numbers, was estimated with a standard heritability formula. The test measures level I mental ability--the capacity to store and recall, but not ability to elaborate or manipulate stimuli. Subjects were 35 monozygotic (MZ) twins and 35 same-sex dizygotic…

The several statistical methods described for detecting test bias in terms of various internal features of a person's test performances and the test's construct validity can be applied to any groups in the population. But the evidence regarding groups other than U.S. blacks and whites is either lacking or is still too sketchy to permit any strong…

The uses of data on siblings for educational and psychological research purposes are explained. Examples are based on empirical data. Five types of research problems, using sibling data, are explored: (1) statistical control of family background variance in psychological or educational studies which use analysis of covariance (ANCOVA) or multiple…