Significant Factor Score Variability and the Validity of the WISC-III Full Scale IQ in Predicting Later Academic Achievement

Abstract

The purpose of this study was to investigate the validity of the WISC-III (Wechsler, 1991) Full Scale IQ (FSIQ) scores in predicting later academic achievement given significant variability among any of the four WISC-III factor scores. Taken from an archival data set, the sample was composed of 6- to 13-year-old students who were twice evaluated for special education eligibility over approximately a 3-year retest interval. Participants were separated into two groups based on the presence or absence of significant factor score variability and then matched across groups on disability, FSIQ, age, sex, and ethnicity. The results of hierarchical multiple regression analyses indicated that the Full Scale IQ was a valid predictor of academic achievement scores even in the presence of significant factor score variability.

Key words:

• academic achievement
• factor score variability
• intelligence
• test interpretation

Notes

Note. FSIQ = Full-Scale IQ, VC= = Comprehension, PO = Perceptual Organization, FD = Freedom from Distractibility, PS = Processing Speed. All correlations were significant at the p < .01 level.

^aAll IQ score correlations are concurrent. IQ-Achievement score correlations are longitudinal.

^aStatistical significance was calculated based on discrepancies reported in Table B.1 on page 261 in the WISC-III manual (Wechsler, 1991). Factor index difference scores required for significance were taken from the “All Ages” category according to a .05 level of significance.

Note. R ² Δ = R ² change. FSIQ (Full-Scale IQ) was centered by subtracting the sample mean from each FSIQ score. Profile status was dummy coded with the presence of significant factor score discrepancy coded as 1 and the absence of such discrepancy coded as 0.

∗p < .01.

∗p < .01.