WISC-R stability and re-evaluation of learning-disabled students

This study investigated the temporal stability of WISC-R IQ scores for learning-disabled subjects (N = 113). All study subjects were administered the WISC-R for an initial evaluation (M age = 8 years, 3 months) and a follow-up re-evaluation (M age = 11 years, 7 months). Pearson product-moment correlations yielded coefficients that were considerably lower than those previously reported: r = .55, p less than .001 for the Verbal IQs; r = .63, p less than .001 for the Performance IQs; and r = .58, p less than .001 for the Full Scale IQs. Results of t-test analyses indicated that only the Verbal IQ scores were significantly different when the initial evaluation (M = 89.4) was compared to the re-evaluation (M = 85.3), p less than .001. The results suggest that the WISC-R may be less stable for the learning-disabled population than for other groups and that the average 3-year test-retest time lapse was an influential factor in the reduced reliability of this instrument.