Linear versus normalized T scores as standardized neuropsychological test scores

In this paper we present and discuss standardized T score systems for neuropsychological test data. Both linear and normalized T scores were calculated for 141 normal subjects and a group of 141 patients with diffuse or focal brain damage. Many standard neuropsychological tests have skewed raw score and linear T score distributions, and we argue that normalized T scores have practical advantages because they permit simple descriptions of both patient groups and individual test score distributions. We also argue that skewness can be partially explained by ceiling effects and other test construction artefacts and that skewed raw score distributions do not necessarily reflect skewed distributions of the underlying mental abilities. Consequently, use of normalized T scores seems appropriate in many research and clinical contexts.