A Reply to Kishor: Choosing the Right Metric

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Abstract
Kishor (this issue) claims that the Stanford Achievement Test normed on deaf children (SAT-d) scaled scores offer the best metric for estimating IQ-Achievement correlations in samples of deaf children. We argue that he is partly right and mainly wrong. We agree with Kishor that SAT-d grade equivalents are inappropriate, although we could not replicate his results. However, Kishor's simulations are logically and empirically flawed and, therefore, cannot address the relative value of SAT-d metrics. More appropriate simulations show (a) that in homogeneous age samples, all SAT-d metrics yield similar results, and (b) in heterogeneous age samples, age-referenced scores are superior to scaled scores and grade equivalents for estimating “true” IQ-Achievement correlations. Our results suggest two practical implications: (1) researchers should use age-based percentiles for achievement if they also use age-referenced IQs, and (b) available studies underestimate IQ-Achievement correlations in samples of deaf children.