Application of single-level and multi-level Rasch models using the lme4 package.

The aim of the article is to illustrate how researchers may use the lme4 package to run multilevel Rasch models. The lme4 package is a popular open-source software and is frequently used by researchers around the world to fit generalized mixed-effects models with crossed or partially crossed random effects. The article starts with a short discussion of the reasons why a researcher might, sometimes, be motivated to use a multi-level Rasch model and presents a practical example using empirical data. The main features of the lme4 package are presented, and finally, the paper presents information about other open-source software that could alternatively be used to fit multi-level Rasch models.