Construct Validity and Measurement Invariance of the Peabody Picture Vocabulary Test–III Form A

Abstract

The aim of this study was to apply the Rasch model to an analysis of the psychometric properties of the Peabody Picture Vocabulary Test--III Form A (PPVT--IIIA) items with struggling adult readers. 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--IIIA items was evaluated using the Winsteps software. 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 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. 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.

ACKNOWLEDGMENTS

This study was supported by the Eunice Kennedy Shriver National Institute of Child Health and Human Development, the National Institute for Literacy, and the U.S. Department of Education---grant # R01 HD43801. We thank Mike J. Linacre for valuable suggestions and two anonymous reviewers for constructive feedback on the earlier version of this article.

Notes

¹This sample was part of a larger study on struggling adult readers.

²An anonymous reviewer raised this important point, and we are appreciative.

³This is also a point raised by an anonymous reviewer.