Incremental Validity of WISC-IV[superscript UK] Factor Index Scores with a Referred Irish Sample: Predicting Performance on the WIAT-II[superscript UK]

• Published in: British journal of educational psychology 2014-12, Vol.84 (4), p.667-684
• Main Authors: Canivez, Gary L, Watkins, Marley W, James, Trevor, Good, Rebecca, James, Kate
• Format: Article
• Language: English
• Subjects: Academic Achievement; Achievement; Achievement Tests; Adolescent; Adolescents; Child; Children; Educational Status; Effect Size; Female; Foreign Countries; Humans; Intelligence Tests; Ireland; Learning Disorders - diagnosis; Learning Disorders - psychology; Male; Multiple Regression Analysis; Predictive Validity; Psychometrics - statistics & numerical data; Reference Values; Referral and Consultation; Reproducibility of Results; Scores; Statistical Significance; Test Validity; Wechsler Individual Achievement Test; Wechsler Intelligence Scale for Children; Wechsler Scales - statistics & numerical data
• ISSN: 0007-0998
• DOI: 10.1111/bjep.12056

Background: Subtest and factor scores have typically provided little incremental predictive validity beyond the omnibus IQ score. Aims: This study examined the incremental validity of Wechsler Intelligence Scale for Children-Fourth UK Edition (WISC-IV[superscript UK]; Wechsler, 2004a, "Wechsler Intelligence Scale for Children-Fourth UK Edition", Harcourt Assessment, London, UK) and factor index scores in predicting academic achievement on the Wechsler Individual Achievement Test-Second UK Edition (WIAT-II[superscript UK]; Wechsler, 2005a, "Wechsler Individual Achievement Test-Second UK Edition", Pearson, London, UK), beyond that predicted by the WISC-IV[superscript UK] FSIQ. Sample: The sample included 1,014 Irish children (ages 6-0 to 16-9) who were referred for evaluation of learning difficulties. Method: Hierarchical multiple regression analyses were used with the WISC-IV[superscript UK] FSIQ (Block 1) and factor index scores (Block 2) as predictors and WIAT-II[superscript UK] subtest and composite scores as dependent variables. Results: The WISC-IV[superscript UK] FSIQ accounted for statistically significant and generally large portions of WIAT-II[superscript UK] subtest and composite score variance. WISC-IV[superscript UK] factor index scores combined to provide statistically significant increments in prediction of most WIAT-II[superscript UK] subtest and composite scores over and above the FSIQ; however, the effect sizes were mostly small as previously observed (i.e., Canivez, 2013a, "Psychol. Assess.", 25, 484; Glutting "et al.", 2006, "J. Spec. Educ.", 40, 103; Nelson "et al.", 2013, "Psychol. Assess.", 25, 618). Individually, the WISC-IV[superscript UK] factor index scores provided small "unique" contributions to predicting WIAT-II[superscript UK] scores. Conclusion: This, in combination with studies of apportioned variance from bifactor confirmatory factor analysis (Watkins et al., 2013, "Int. J. Sch. Educ. Psychol.", 1, 102), indicated that the WISC-IV[superscript UK] FSIQ should retain the greatest weight in WISC-IV[superscript UK] interpretation.