Motivated from the stochastic representation of the univariate zero-inflated Poisson (ZIP)
random variable, the authors propose a multivariate ZIP distribution, called as Type I
multivariate ZIP distribution, to model correlated multivariate count data with extra zeros.
The distributional theory and associated properties are developed. Maximum likelihood
estimates for parameters of interest are obtained by Fisher’s scoring algorithm and
the expectation–maximization (EM) algorithm, respectively. Asymptotic and bootstrap
confidence intervals of parameters are provided. Likelihood ratio test and score test are
derived and are compared via simulation studies. Bayesian methods are also presented if
prior information on parameters is available. Two real data sets are used to illustrate the
proposed methods. Under both AIC and BIC, our analysis of the two data sets supports the
Type I multivariate zero-inflated Poisson model as a much less complex alternative with
feasibility to the existing multivariate ZIP models proposed by Li et al. (Technometrics,
29–38, Vol 41, 1999).