Running head: DIAGNOSTIC UTILITY SCATTER 1 Evidence-based assessment and Cognitive Profile Scatter: Clinical Acumen or Clinical Illusion?

Within the professional literature, it is frequently suggested that interpretation of cognitive profile scatter may be useful for clinical and/or diagnostic decision-making. To wit, Hale and colleagues (2008) posit that cognitive scatter is a defining characteristic of learning disabilities and that individuals with learning disabilities may have higher levels of scatter than normal controls. To investigate the tenability of this claim, the present study employed diagnostic efficiency statistics and other psychometric methods for examining the utility of proposed diagnostic indicators (e.g., receiver operative characteristic curve, Bayesian nomogram) to determine the degree to which cognitive scatter accurately discriminated between individuals with and without a known learning disability diagnosis in the Kaufman Assessment Battery for Children-Second Edition (KABC-II; Kaufman & Kaufman, 2004a) normative sample. Results indicated that the diagnostic utility of cognitive profile scatter was no better than chance regardless of the level of scatter that was observed. The current negative results suggest that practitioners who interpret cognitive profile scatter may risk diagnostic overconfidence and in the case of SLD identification, unacceptable levels of false positive decisions attributable to error. Implications for evidence-based assessment in clinical and school psychology are discussed.