Using the eRm package for Rasch modeling

The “extended Rasch modeling” (eRm) package in R provides users with a comprehensive set of tools for Rasch modeling for scale evaluation and general modeling. We provide a brief introduction to Rasch modeling followed by a review of literature that utilizes the eRm package. Then, the key features of the eRm package for scale evaluation are reviewed. The ease of use and the advantages of the R environment make the eRm package an appealing free option for rigorous Rasch modeling. We demonstrate the functionality with a small example using data from the Rosenberg Self-Esteem scale. Using these data we show how to 1) fit dichotomous and polytomous Rasch models, 2) obtain key figures (e.g., item characteristic curves and person-item maps) to aid model assessment , 3) assess dimensionality, and 4) obtain item fit statistics.