A comparison of three intelligence tests for the assessment of mental retardation

Thirty-six mentally retarded adolescents were administered the Wechsler Intelligence Scale for Children (WISC), the Peabody Picture Vocabulary Test (PPVT), and the Slosson Intelligence Test (SIT) to determine reliability and comparable performance among the three intelligence tests. Correlations as a function of IQ and MA, by sex, were computed among the three tests. All were significant (p less than .01), but the WISC and SIT had consistently higher relationships than any other comparisons on both IQ and MA. Analyses also indicated that the PPVT produced higher IQ scores than the WISC or SIT and that MA in the PPVT was influenced by the previous administration of the SIT. It was concluded that, as a screening device, the SIT is more reliable and approximates WISC scores more consistently than the PPVT.