MIXZIP 1.0 for Mixed-effects Zero-Inflated Poisson (ZIP) Regression
mixzip1.exe (816 KB)

MIXZIP provides the maximum marginal likelihood estimates of mixed-effects Zero-Inflated Poisson (ZIP) regression models. In the context of a regression model, the ZIP model allows one to estimate one set of regression coefficients for use or non-use of services and a separate set of regression coefficients for the amount of services used, conditional on their use. The mixed-effects case is a generalization of the ZIP model for analysis of longitudinal and / or clustered service utilization data where the data within clusters are assumed to be dependent. MIXZIP uses marginal maximum likelihood estimation, utilizing a Newton-Raphson iterative solution. Currently, the program allows for single but separate random effects for both logistic and Poisson components of the model.