Comparability of IQ Scores on Five Widely Used Intelligence Tests

Abstract

Statistical comparability of verbal and nonverbal IQ scores from five widely used intelligence tests (Lorge-Thorndike, California, Henmon-Nelson, Kuhlmann-Anderson, and Otis) was established by equating to a common anchor test by equipercentile methods in grades four, seven, and ten in 41 school systems. In general, correlations among IQ scores were well below equivalent-forms reliability coefficients, which indicates that the various tests are measuring somewhat different traits. Differences in comparable IQ's varied from test to test and from grade to grade and with IQ level. At IQ 70 on the anchor battery, the average difference was 3.1 IQ points; at IQ 100, 2.2 IQ points; and at IQ 130, 3.1 IQ points.