Relationship of state educational criteria and demographic variables to school-system prevalence of mental retardation.

A survey of state departments of education revealed wide variations in mental retardation terminology, definition, and classification variables. The relationship of survey variables and demographic characteristics of states with school-system prevalence of mental retardation was analyzed. Survey variables such as mental retardation definition, adaptive behavior measurement, and IQ cutoff score were largely unrelated to school-system prevalence. Demographic characteristics based on summary data for states on variables such as per capita income, educational level, and rate of illiteracy were highly related to school-system prevalence. Caution was recommended in interpretation of results based on ecological correlations, i.e., correlations based on group summaries rather than individual data. The results were seen as further indication of the relative, social-system nature of mild mental retardation.