equateIRT Package in R

Equating test scores between different achievement test versions is important to assure comparability between test takers' scores. As many items are modelled with item response theory (IRT), it makes sense to also equate the test scores with IRT equating methods. The equateIRT package in R provides a set of functions which implements IRT equating methods including newer extensions. This paper summarizes some of the advances in equating with IRT, reviews the equateIRT package, and demonstrates, through two illustrative examples, some of the key features of the package.