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The Other Side of the Bell Curve: Multivariate Base Rates of High Scores on the Delis-Kaplan Executive Function System

Published online by Cambridge University Press:  15 November 2019

Justin E. Karr*
Affiliation:
Department of Psychiatry, Harvard Medical School, Boston, MA02215, USA Department of Physical Medicine and Rehabilitation, Harvard Medical School, Boston, MA02129, USA Spaulding Rehabilitation Hospital, Spaulding Research Institute, Charlestown, MA02129, USA Home Base, A Red Sox Foundation and Massachusetts General Hospital Program, Boston, MA02129, USA
Mauricio A. Garcia-Barrera
Affiliation:
Department of Psychology, University of Victoria, Victoria, British Columbia V8P 5C2, Canada
James A. Holdnack
Affiliation:
Research and Statistics Consultant, Bear, DE 19701, USA
Grant L. Iverson
Affiliation:
Department of Physical Medicine and Rehabilitation, Harvard Medical School, Boston, MA02129, USA Spaulding Rehabilitation Hospital, Spaulding Research Institute, Charlestown, MA02129, USA Home Base, A Red Sox Foundation and Massachusetts General Hospital Program, Boston, MA02129, USA
*
*Correspondence and reprint requests to: Justin E. Karr, 79/96 Thirteenth Street, Charlestown Navy Yard, Charlestown, MA 02129, USA. E-mail: [email protected]

Abstract

Objective:

Previous researchers have examined the frequency at which healthy participants obtain one or more low scores on neuropsychological test batteries, proposing five psychometric principles of multivariate base rates: (a) low scores are common, with their frequency contingent on (b) the low score cutoff used, (c) the number of tests administered/interpreted, and (d) the demographic characteristics and (e) intelligence of participants. The current study explored whether these principles applied to high scores as well, using the Delis-Kaplan Executive Function System (D-KEFS).

Method:

Multivariate base rates of high scores (≥75th, ≥84th, ≥91st, ≥95th, and ≥98th percentiles) were derived for a three-test, four-test, and full D-KEFS battery, using the adult portion of the normative sample (aged 16–89 years; N = 1050) stratified by education and intelligence. The full D-KEFS battery provides 16 total achievement scores (primary indicators of executive function).

Results:

High scores occurred commonly for all batteries. For the three-test battery, 24.1% and 12.4% had 1 or more scores ≥95th percentile and ≥98th percentile, respectively. High scores occurred more often for longer batteries: 61.6%, 72.9%, and 87.8% obtained 1 or more scores ≥84th percentile for the three-test, four-test, and full batteries, respectively. The frequency of high scores increased with more education and higher intelligence.

Conclusions:

The principles of multivariate base rates also applied to high D-KEFS scores: high scores were common and contingent on the cutoff used, number of tests administered/interpreted, and education/intelligence of examinees. Base rates of high scores may help clinicians identify true cognitive strengths and detect cognitive deficits in high functioning people.

Type
Regular Research
Copyright
Copyright © INS. Published by Cambridge University Press, 2019

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