Ethnicity, geographic locale, age, sex, and urban-rural residence as variables in the prevalence of mild retardation.

The Wechsler-Intelligence Scale for Children-Revised (WISC-R) was administered to 950 of a stratified random sample of 1,040 children in Pima County, Arizona. The sample was stratified for ethnicity (Anglo, Black, Mexican-American, and Papago Indian), urban-rural residence, sex, and grade level. The three WISC-R IQ scores and cutoff points of 69 and 75 were used in comparisons of prevalence of mild mental retardation. This prevalence was significantly related to ethnicity and geographic locale. Sex, urban-rural residence, and grade level were not related to prevalence.