Confirmatory Factor Analysis of the WIAT-III in a Referral Sample

The Wechsler individual achievement test, third edition (WIAT-III) is a popular individually administered achievement battery. Despite its ubiquity in assessment practice, scant research into its structure exists. We analyzed the structure of the WIAT-III in a sample of students in Grades 3-12 referred for special education evaluations (n = 355). Using confirmatory factor analysis, we evaluated the fit of the factor structure assumed by the composite scores provided by the test publisher. We then compared that model to alternative first-order, second-order and bifactor models in an exploratory fashion. Results demonstrated that the publisher implied model does not capture the structure of the WIAT-III. Instead subtests appear related to each other based on both their domain of academic performance and in other shared abilities. Implications for practice are discussed.