How a regression artifact makes ICFs/MR look ineffective.
Based on a simple matched-control group quasi-experiment, Conroy (1996) concluded that small ICFs for persons with mental retardation have negative quality-of-life impacts.
Our analysis of Conroy's design suggests, in contrast, that the reported effect is a pure regression artifact.
The flaw in Conroy's design is selecting a control group on the basis of pretest matching.
Although selecting a subsample of controls by matching on static characteristics such as age or gender can reduce the confounding influence of these variables, selection on the basis of pretest scores leads invariably to a large, spurious effect.
The literature on this issue dates back a century, with warnings against pretest matching by Galton, Thorndike, McNemar, Stanley, Campbell, Cronbach, and Cook.
We reviewed this historical literature and then used a Monte Carlo experiment to estimate the spurious effect that Conroy would observe from pretest matching alone.
The magnitude of the artifact is as large as the quality-of-life reduction that Conroy attributed to the effects of living in an ICF.
We discussed the methodological logic involved in matching and the broader policy issues raised by this evaluation.
Mots-clés Pascal : Arriération mentale, Qualité vie, Besoin utilisateur, Service santé, Santé mentale, Analyse statistique, Méthodologie, Etude critique, Homme, Déficience intellectuelle, Trouble développement
Mots-clés Pascal anglais : Mental retardation, Quality of life, User need, Health service, Mental health, Statistical analysis, Methodology, Critical study, Human, Intellectual deficiency, Developmental disorder
Notice produite par :
Inist-CNRS - Institut de l'Information Scientifique et Technique
Cote : 98-0314802
Code Inist : 002B18H05B. Création : 27/11/1998.