Illusions of Meaning in the Ipsative Assessment of Children's Ability

Abstract

In this study, we analyze the relative efficacy of normative and ipsative measures for the study of intra- and interindividual differences in child ability. With the use of representative data sets, including the WISC-R national standardization sample, purely ipsatized (or deviational ipsative) subtest scores were contrasted with conventional norm-based scores in terms of the evidential and consequential bases for validity. Internal and external evidence for validity was assessed for relative convergence of ability attributes, short- and long-term stability, and predictive efficiency. Comparative utility of each type of measure was explored for theoretical relevance, applicability in measurement work, and assessment of individualized intervention outcomes. Ipsative ability measures were found to be uniformly inferior to their normative counterparts, with ipsative measures conveying no uniquely useful information and otherwise impeding the versatility of assessment.