equateMultiple: An R Package to Equate Multiple Forms

Abstract

Item response theory (IRT) provides a framework for modeling the responses given to a test or questionnaire, which are assumed to depend on an underlying latent variable and on some item parameters. Due to identifiability issues, when the parameters are estimated separately on different datasets, the estimates of the item parameters and the predicted values of the latent variable are not directly comparable. Equating is a statistical procedure that can be used to convert these values to a common metric and to obtain comparable test scores. The R package equateMultiple implements methods to link the parameters estimated on many different datasets. After briefly reviewing the IRT models and the equating methods, this article illustrates the use of the package.