Incremental criterion validity of WAIS–IV factor index scores: Relationships with WIAT–II and WIAT–III subtest and composite scores.
The present study examined the incremental validity of Wechsler Adult Intelligence Scale–4th Edition (WAIS–IV; Wechsler, 2008a) factor index scores in predicting academic achievement on the Wechsler Individual Achievement Test–2nd Edition (WIAT–II; Psychological Corporation, 2002a) and on the Wechsler Individual Achievement Test–3rd Edition (WIAT–III; Wechsler, 2009a) beyond that predicted by the WAIS–IV Full Scale IQ (FSIQ). As with previous intelligence test incremental validity studies, the WAIS–IV FSIQ accounted for statistically significant and generally large portions of WIAT–II and WIAT–III subtest and composite score variance. WAIS–IV factor index scores combined to provide statistically significant increments in variance accounted for in most WIAT–II and WIAT–III subtest and composite scores over and above the FSIQ score; however, the effect sizes ranged from trivial to medium as observed in investigations with other intelligence tests (i.e., Glutting, Watkins, Konold, & McDermott, 2006; Youngstrom, Kogos, & Glutting, 1999). Individually, the WAIS–IV factor index scores provided trivial to small unique contributions to predicting WIAT–II and WIAT–III scores. This finding indicated that the FSIQ should retain primacy and greatest interpretive weight in WAIS–IV interpretation, as previously indicated by WAIS–IV subtest variance partitions form hierarchical exploratory factor analyses (Canivez & Watkins, 2010a, 2012b). (PsycINFO Database Record (c) 2013 APA, all rights reserved)