The Exchangeability of IQs: Implications for Professional Psychology

IQs are important measures in the practice of psychology. Psychologists may frequently expect that IQs from different test batteries are reasonably exchangeable as measures of general intelligence. Results presented in this article provide evidence that different test batteries produce less similar IQs for samples of school-age children and undergraduate students than may have been expected. In fact, psychologists can anticipate that 1 in 4 individuals taking an intelligence test battery will receive an IQ more than 10 points higher or lower when taking another battery. Resulting suggestions for practice include carefully choosing batteries that provide representative sampling of specific abilities, differential weighting, or both; attending to unreliability in measurement; closely monitoring behaviors that undermine assessment of general intelligence; and considering the benefits of obtaining multiple IQs when such scores are used to make high-stakes diagnostic or eligibility decisions. © 2008 American Psychological Association