Non-equivalence of WPPSI, WPPSI-R, and WISC-R scores

The WPPSI-R, WISC-R, and WPPSI were administered in a counterbalanced design to 72 children, between the ages of 5 years, 11 months and 6 years, 8 months, in order to determine their equivalence by testing the equality of means, variances, and covariances based on scaled scores and IQs. The results indicated that the three scales were not equivalent with respect to any of the IQs because they did not meet one or more of the criteria. The relative magnitudes of the mean IQs on the three scales were in accord with the predicted order: highest IQs on WPPSI, next highest on WISC-R, and the lowest on WPPSI-R. Results were discussed in the context of the secular inflation in IQs and the corresponding compensatory deflation built into the normative data of the new versions.