Pick Your Poisson: A Tutorial on Analyzing Counts of Student Victimization Data

Abstract

School violence research is often concerned with infrequently occurring events such as counts of the number of bullying incidents or fights a student may experience. Analyzing count data using ordinary least squares regression may produce improbable predicted values, and as a result of regression assumption violations, result in higher Type I errors. Count data are optimally analyzed using Poisson-based regression techniques such as Poisson or negative binomial regression. We apply these techniques to an example study of bullying in a statewide sample of 290 high schools and explain how Poisson-based analyses, although less familiar to many researchers, can produce findings that are more accurate and reliable, and are easier to interpret in real-world contexts.