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SAS Program for MCMC Scoring of PPVT Item Data (Hoffman et al., 2012)

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posted on 2021-12-18, 00:17 authored by Lesa Hoffman, Jonathan Templin, Mabel L. Rice
Purpose: The present work describes how vocabulary ability as assessed by 3 different forms of the Peabody Picture Vocabulary Test (PPVT; Dunn & Dunn, 1997) can be placed on a common latent metric through item response theory (IRT) modeling, by which valid comparisons of ability between samples or over time can then be made.
Method: Responses from 2,625 cases in a longitudinal study of 697 persons for 459 unique PPVT items (175 items from Peabody Picture Vocabulary Test—Revised [PPVT–R] Form M [Dunn & Dunn, 1981], 201 items from Peabody Picture Vocabulary Test—3 [PPVT–3] Form A [Dunn & Dunn, 1997], and 83 items from PPVT–3 Form B [Dunn & Dunn, 1997]) were analyzed using a 2-parameter logistic IRT model.
Results: The test forms each covered approximately ±3 SDs of vocabulary ability with high reliability. Some differences between item sets in item difficulty and discrimination were found between the PPVT–3 Forms A and B.
Conclusions: Comparable estimates of vocabulary ability obtained from different test forms can be created through IRT modeling. The authors have also written a freely available SAS program that uses the obtained item parameters to provide IRT ability estimates given item responses to any of the 3 forms. This scoring resource will allow others with existing PPVT data to benefit from this work as well.


This research was funded by National Institutes of Health Grants P30DC005803, R01DC001803, and R01DC005226 (awarded to Mabel L. Rice) and by University of Kansas Intellectual and Developmental Disabilities Research Center Grant P30HD002528.


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