Construct Validity and Measurement Invariance of the Peabody Picture Vocabulary Test-III Form A in the Performance of Struggling Adult Readers: Rasch Modeling.

PURPOSE

The aim of this study was to apply the Rasch model to an analysis of the psychometric properties of the PPVT-III Form A items with struggling adult readers. METHODS: The PPVT-IIIA was administered to 229 African-American adults whose isolated word reading skills were between third and fifth grades. Conformity of the adults' performance on the PPVT-III items was evaluated using the Winsteps software. RESULTS: Analysis of all PPVT-IIIA items combined did not fully support its use as a useful measure of receptive vocabulary for struggling adult readers who were African Americans. To achieve an adequate model fit, items 73 through item 156 were analyzed. The items analyzed showed adequate internal consistency reliability, unidimensionality, and freedom from differential item functioning for ability, gender, and age, with a minor modification. DISCUSSION: With an appropriate treatment of misfit items, the results supported the measurement properties, internal consistency reliability, unidimensionality of the PPVT-IIIA items, and measurement invariance of the test across subgroups of ability, age, and gender.