Viariability in Clinical Classification of Raw Test Scores Across Normative Data Sets

Sampling differences and other sources of measurement error result in variation between normative data sets reported for the same test; however, no research has examined the degree to which classification of a specific score may be affected by discrepancies across norms. The present study applies different sets of published normative data to test protocols of 12 men and women of various ages and levels of education. The tests included in the fictitious assessment battery are used routinely by neuropsychologists according to Butler, Retzlaff, and Vanderploeg (1991) and have at least two sets of published norms. Our findings indicate that interpretation of performance on neuropsychological tests is frequently and dramatically affected by sampling differences across normative data sets. Suggestions for the selection of normative data sets for clinical assessments and the development of comprehensive normative data sets are offered.