Does High Scatter on the Wechsler Adult Intelligence Scale-Fourth Edition General Ability Index Reduce Validity in Predicting Wechsler Memory Scale-Fourth Edition indexes?

We examined whether significant scatter in WAIS-IV GAI will reduce its validity to predict performance on WMS-IV indexes. Participants were 330 individuals with neurological, psychiatric, or neurodevelopmental disorders and 59 referrals who were found to be free of a diagnosable disorder. For VCI > PRI, 59.32% were significant at p < .05 and 12.29% were >22 points. For VCI < PRI, 48.37% were significant at p < .05 and 7.19% were >22 points. Inter-subtest scatter across GAI subtests indicated 82.26% of individuals had a significant scatter range and 13.88% had an unusually large range (≥8). For the VCI, 49.10% had significant scatter (≥3) and 12.08% had an unusually large scatter range (≥5). On the PRI, 43.19% had a significant scatter range (≥4) and 12.85% had an unusually large degree of scatter (≥6). Moderation analyses revealed GAI was a significant predictor of each WMS-IV index. The interaction term of GAI with GAI scatter was not significant for any indexes, indicating that regression equations for predicting WMS-IV scores from GAI did not vary significantly across levels of scatter. Estimation of WMS-IV indexes from the GAI is justified even when significant VCI-PRI discrepancies are present and there is unusual variability across the GAI subtests.