Measurement Reliability,the Spearman–Jensen Effect and the Revised Thorndike Model of Test Bias

The Thorndike model of test fairness has recently been revised and used to argue that cognitive ability tests are biased against certain groups of test‐takers because ability tests show larger mean differences across racial groups than do job performance measures. We discuss two critical factors that confound this new version of Thorndike's model, making it susceptible to false indications of test bias. Those factors are (a) measurement error (i.e., reliability) in both the predictor and criterion and (b) the Spearman–Jensen effect (i.e., the well‐documented effect that group differences in observed g‐saturated measures are directly proportional to the degree the manifest indicator reflects g). Finally, because the Spearman–Jensen effect is not well known within the applied literature, we present a brief simulation to better elucidate the implications of the Spearman–Jensen effect for personnel selection in general, and claims of bias in cognitive ability testing in particular.