title: Incremental validity of WISC-IV(UK) factor index scores with a referred Irish sample: predicting performance on the WIAT-II(UK.).
abstract: BACKGROUND
  Subtest and factor scores have typically provided little incremental predictive validity beyond the omnibus IQ score.
  
  
  OBJECTIVE
  This study examined the incremental validity of Wechsler Intelligence Scale for Children - Fourth UK Edition (WISC-IV(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(UK) ; Wechsler, 2005a, Wechsler Individual Achievement Test-Second UK Edition, Pearson, London, UK), beyond that predicted by the WISC-IV(UK) FSIQ.
  
  
  METHODS
  The sample included 1,014 Irish children (ages 6-0 to 16-9) who were referred for evaluation of learning difficulties.
  
  
  METHODS
  Hierarchical multiple regression analyses were used with the WISC-IV(UK) FSIQ (Block 1) and factor index scores (Block 2) as predictors and WIAT-II(UK) subtest and composite scores as dependent variables.
  
  
  RESULTS
  The WISC-IV(UK) FSIQ accounted for statistically significant and generally large portions of WIAT-II(UK) subtest and composite score variance. WISC-IV(UK) factor index scores combined to provide statistically significant increments in prediction of most WIAT-II(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(UK) factor index scores provided small unique contributions to predicting WIAT-II(UK) scores.
  
  
  CONCLUSIONS
  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(UK) FSIQ should retain the greatest weight in WISC-IV(UK) interpretation.
authors.affiliation: Department of Psychology, Eastern Illinois University, Charleston, Illinois, USA.
authors.forename: Gary L
authors.initials: GL
authors.lastname: Canivez
authors.forename: Marley W
authors.initials: MW
authors.lastname: Watkins
authors.forename: Trevor
authors.initials: T
authors.lastname: James
authors.forename: Rebecca
authors.initials: R
authors.lastname: Good
authors.forename: Kate
authors.initials: K
authors.lastname: James
mesh_terms: D000124:Achievement; D000293:Adolescent; D002648:Child; D004522:Educational Status; D005260:Female; D006801:Humans; D007494:Ireland; D007859:Learning Disabilities / Q000175:diagnosis* / Q000523:psychology; D008297:Male; D011594:Psychometrics / Q000706:statistics & numerical data; D012016:Reference Values; D012017:Referral and Consultation; D015203:Reproducibility of Results; D014888:Wechsler Scales / Q000706:statistics & numerical data*
keywords: WIAT-IIUK; WISC-IVUK; achievement prediction; construct validity; hierarchical multiple regression; incremental validity