In this digital ITEMS module, Dr. Jodi M. Casabianca provides a primer on the hierarchical rater model (HRM) and the recent expansions to the model for analyzing raters and ratings of constructed responses. In the first part of the module, she establishes an understanding of the nature of constructed responses, the rating process and the common rater errors or rater effects originating from the rating process. In the second part of the module, she compares traditional measures for analyzing raters to item response theory (IRT) measures and discusses various IRT rater models. In the third section, she discusses longitudinal and multidimensional extensions and their foundations in different combinations of IRT and signal detection models. The module contains audio-narrated slides, quizzes with feedback, and additional resources such as a glossary and reference documents.