Monday, October 12, 2009

More voodoo psychometrics in Atkins MR death penalty cases? This time adaptive behavior

Voodoo psychometrics strikes again!

A few days ago I made a post (and a subsequent brief FYI follow-up post)  regarding a number of theoretical and psychometric issues that surfaced in the Maldonado (2009) Atkins MR death penalty court decision (click here and here).  It was my opinion that a number of questionable arguments and decisions had been made re: the entirety of the psychometric intelligence test data available in the Maldonado (2009) decision. I won't repeat them here.

Probably my biggest criticism was the use of a non-empirical, unvalidated n=1 psychologist clinical procedure to upwardly adjust IQ scores based on educational and cultural background variables.  Today I learned  that similar "social-cultural" upward adjustment of adaptive behavior scale scores, which are the foundation of the second prong of the determination of mental retardation (or not) in Atkins cases, has also occurred in a number of Atkins cases.  This time I was able to locate an article by Denkowski and Denkowski (2008) that outlined the logic and reasoning for the recommended "systematic" procedure.  I read it in psychometric disbelief!

There is no reason for me to outline my psychometric criticisms, as a number of authors replied with most of the arguments I would have made.  These response, in the same journal, are by Widaman & Siperstein (2009) and Olley (2009) (click here for post re: AB-related chapter by Olley &Cox, 2008). Denkowski and Denkowski (2009) then reply.

As an applied psychometrician, I concur with most of the reactions and arguements of Widaman, Siperstein and Olley.  There is simply insufficent scientifc and psychometric grounds for the upward adjustment of AB scores as outlined.  Yes, psychologists are trained to use clinical adjustment when interpreting test scores, and I so invoked such judgement when conducting countless intellectual assessments during my years as a practicing school psychologist, but clinical judgement is not the same as the development of special score adjustments of nationally standardized psychological instruments based primarily on logic and reason.

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