Score test for homogeneity of dispersion in generalized Poisson mixed models with excess zeros |
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Authors: | Feng-Chang Xie Jin-Guan Lin Bo-Cheng Wei |
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Affiliation: | 1. School of Mathematical Sciences and Institute of Finance and Statistics, Nanjing Normal University, Nanjing, China;2. Department of Mathematics, Southeast University, Nanjing, China |
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Abstract: | In many applications, the clustered count data often contain excess zeros and the zero-inflated generalized Poisson mixed (ZIGPM) regression model may be suitable. However, dispersion in ZIGPM is often treated as fixed unknown parameter, and this assumption may be not appropriate in some situations. In this article, a score test for homogeneity of dispersion parameter in ZIGPM regression model is developed and corresponding test statistic is obtained. Sampling distribution and power of the score test statistic are investigated through Monte Carlo simulation. Finally, results from a biological example illustrate the usefulness of the diagnostic statistic. |
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Keywords: | Dispersion Generalized Poisson mixed model Score test |
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