count data

Model Perspective

Aug 1, 2022 · Fundamentals

When to Use Poisson vs. Negative Binomial Regression: A Practical Guide

Poisson regression models count data assuming equal mean and variance, while negative binomial regression handles over‑dispersion by adding a gamma‑distributed heterogeneity term; this article explains their assumptions, likelihoods, interpretation of incidence rate ratios, and guidance on choosing the appropriate model with robust standard errors.