Social Class and Test Performance: Comparative Validity of the Peabody with the WISC and WISC-R for Two Socioeconomic Groups

Comparability of IQs yielded by the Peabody and the revised Wechsler scale, the WISC-R, is important to interpret IQ estimates obtained from these two scales. In the present study, 40 normal 10-yr.-old children (20 male and 20 female, half of whom were from high and half from low socioeconomic status) were compared for performance on the Peabody, the WISC and the WISC-R. IQs obtained on Forms A and B of the Peabody correlate highly and, thus, the two Peabody forms are essentially parallel and equivalent forms. Concurrent validity coefficients ranging from .71 to .83 were obtained between the Peabody IQs and Verbal and Full Scale IQs of the WISC and the WISC-R. Much lower validity coefficients were obtained between the Peabody and Performance IQs of the WISC and the WISC-R. Large differences in IQ between children from low socioeconomic backgrounds and those from high socioeconomic backgrounds were obtained on all four tests. The Peabody IQs were closer in magnitude to the WISC-R IQs than to the WISC in the low socioeconomic group. The results support administering the Peabody to children for obtaining valid IQ estimates. Interpretations of Peabody scores in relation to the WISC-R should be somewhat different from those of the Peabody and the WISC, however, in view of the effects of socioeconomic status (and therefore ability level) on estimates of IQ.