On WAIS—R difference scores in a psychiatric sample.

Abstract

This report examines the psychometric integrity of the Wechsler Adult Intelligence Scale-Revised (WAIS-R) subscales, and the differences between them, in a sample of 229 psychiatric patients from 2 community mental health centers (ages 16 to 85). The results verify the overall alpha and split-half reliabilities of the instrument and indicate that greater caution needs to be exercised in clinically evaluating difference scores. Cutoff values presented in the manual appear too low to be of any statistical or diagnostic merit. Distributions for each of the 55 possible difference scores found in this sample are presented and provide a better guide for making nosological determinations.

Base rates of WAIS‐R VIQ–PIQ differences in 1593 psychiatric inpatients

“…Stutts, 1991). Researchers also have reported that specific psychiatric disorders such as depression (Groth-Marnat, 1984;Kaufman, 1990;Kluger & Goldberg, 1990;Pernicano, 1986;Robertson & Taylor, 1985;Sackeim et al, 1992;Zillmer et al, 1991) and schizophrenia spectrum disorders (Pernicano, 1986;Piedmont et al, 1989aPiedmont et al, , 1989b are associated with a VIQ Ͼ PIQ configuration.…”

“…Relatively large VIQ-PIQ difference scores have been reported in mixed samples of psychiatric inpatients (e.g., Piedmont, Sokolove, & Fleming, 1989a, 1989bZillmer, Ball, Fowler, Newman, & 1 For the present discussion, the expression "statistically significant" can be confusing and misleading. Significance tests often are based on means comparisons, such as t tests, for which they refer to the probability that the samples being compared were drawn from the same population.…”

Mental retardation and WAIS‐R difference scores

“…The measurement of specific abilities renders it theoretically possible to interpret subscale scatter for diagnostic purposes (Rapaport et al, 1968). Therefore, WAIS-R subtest scatter per se (Atkinson, 1991a, b;Chelune et al, 1987;Matarazzo & Profitera, 1989;McDermott et al, 1989;Mittenberg et al, 1989;Piedmont et al, 1989b;Watkins et al, 1991), as well as its possible diagnostic implications (Allison et al, 1988;Bornstein et al, 1989;Piedmont et al, 1989aPiedmont et al, , 1989cPiedmont et al, , 1990 have been vigorously explored.…”

“…These statistics enable us to determine the extent to which difference scores can be attributed to measurement error, and the extent to which they reflect true differences across ability levels. Piedmont et al (1989b) published figures for interpreting WAIS-R difference scores based on a sample of 229 psychiatric patients (and recommended fuller exploration of the WAIS-R with more homogeneous clinical samples). Atkinson (1991a) produced a similar table describing the properties of subtest score differences for the WAIS-R standardization sample.…”

“…Atkinson (1991a) produced a similar table describing the properties of subtest score differences for the WAIS-R standardization sample. He argued that the calculations used by McNemar (1957) and Piedmont et al (1989b) were technically incorrect if these authors wished their results to be generalizable beyond the samples upon which they were based. In computing measurement errors for the difference scores (6e(d), McNemar (1957) and Piedmont et al (1989b) used a standard error of measurement that is purely descriptive in nature, one that provides an inflated estimate of the population parameter (see Dudek, 1979, Formula 1;Lord & Novick, 1968).…”