Comparability of the WISC and the WISC-R in normal children of divergent socioeconomic backgrounds

WISC and WISC-R IQs of two groups of normal ten-year-old children from divergent socioeconomic backgrounds (N = 36) were compared in a counterbalanced research design. Generally, all WISC mean IQs were higher than the WISC-R mean IQs for both groups of children. Significantly higher WISC IQs were obtained on the Verbal and Full Scales of the low socioeconomic group and on the Performance and Full Scales of the high socioeconomic group. Correlations between tests for Verbal, Performance, and Full Scale IQs were.95,.79, and.91 for the low socioeconomic group, and.84,.57, and.87 for the high socioeconomic group. Although practice effects did not appear to significantly affect IQs of the low socioeconomic group, various practice effects were observed in the high socioeconomic group. Negative effects were observed for both WISC and WISC-R on the Verbal Scale, whereas positive effects were observed on both Performance and Full Scales in this group. Analysis of simple effects reveals that WISC and WISC-R IQs did not differ significantly upon first administration, but were significantly different upon second administration. Conclusions were drawn that while WISC-R yields a lower IQ estimate than WISC for children of lower ability, results were not so clear for the children of higher ability, due to practice effects which disproportionately favor increases on WISC IQs upon second administration. The greater practice effects found on the WISC have implications for comparisons of the two tests in counterbalanced research designs. Simple randomized or treatment-by-levels design may be more useful in comparisons of the WISC and the WISC-R because of the bias introduced by counterbalanced designs.