Modelling Count Data in Psychological Research: An Applied Tutorial

Abstract

Across subfields of psychology, researchers frequently encounter count variables (i.e., non-negative integer values, which result from counted measurements). Although count variables are common in psychological research (e.g., frequency of behaviours or symptoms), researchers may not be aware of appropriate statistical procedures for modelling and drawing inferences from count data. Specialised regression techniques (i.e., generalised linear models and zero-augmented models) have been developed for the unique properties of count data, but they can seem inaccessible to non-technical audiences because of their departure from more familiar methods. Assuming a basic knowledge of linear regression, this tutorial aims to demystify count regression approaches and empower researchers to apply these methods to their own count data, using free, open-source statistical software (i.e., R). This tutorial takes researchers step-by-step through the implementation of count regression methods in applied research, imparting them with the knowledge to confidently implement these techniques.