Efficiency of Peabody Picture Vocabulary in estimating WISC scores for delinquents.

Abstract

IQs on the Peabody Picture Vocabulary Test for 106 males 13 to 16 yr. and of lower class status were related to WISC IQs (assessed by student examiners) in three different ranges (80–89, 70–79, Below 70) as a function of race. Both group and individual results were consistent with previous data showing the Peabody scale generally overestimates the IQs of retarded subjects. The present results, however, also indicate that the Peabody tended to underestimate the IQs of 34 “Dull Normal” subjects. Thus, there appears to be an interaction between the Peabody, the WISC, and IQ level. Individual analysis corroborated the group analysis in that 77% of the 26 black subjects and 93% of the 15 white subjects in the range below 70 IQ obtained Peabody scores which overestimated Full Scale WISC IQs. In the “Dull Normal” IQ range the Peabody underestimated WISC performance for 89% of the 18 black subjects and 81% of the 16 white subjects. When the Wechsler mean IQ for both blacks and whites was between 60 and 83 the Peabody tended to produce a mean IQ score between 70 and 78. Thus, irrespective of the Wechsler IQ, the mean Peabody IQ showed little variability. The utility of the Peabody in estimating the Wechsler IQ of juvenile offenders is of doubtful value.