SEARCH

SEARCH BY CITATION

Keywords:

  • Count data;
  • Negative binomial;
  • Poisson regression model;
  • Score test;
  • Zero inflation

Summary. Count data often show a higher incidence of zero counts than would be expected if the data were Poisson distributed. Zero-inflated Poisson regression models are a useful class of models for such data, but parameter estimates may be seriously biased if the nonzero counts are overdispersed in relation to the Poisson distribution. We therefore provide a score test for testing zero-inflated Poisson regression models against zero-inflated negative binomial alternatives.