題　目：A Lack-of-Fit Test of Zero-Inflated Poisson Regression Models with Splines 主講人：Prof. Chin-Shang Li (Division of Biostatistics Department of Public Health Sciences, University of California, Davis) 時　間：100年12月2日(星期五)上午10:40-11:30 地　點：交大綜合一館427室 Abstract A zero-inflated Poisson (ZIP) regression model has been extensively used in biomedical studies, criminology, environmental economics and others for the effect of a covariate in count data containing many zeros with a linear predictor. To assess the adequacy of the linear relationship, we approximate the covariate effect with cubic B-splines. The proposed semiparametric ZIP regression model greatly enhances modeling flexibility. The semiparametric model parameters are estimated by maximizing the likelihood function through an expectation-maximization algorithm. A likelihood ratio test is then used to assess the adequacy of the linear relation. A simulation study is conducted to study its power performance. The illustration of the practical use of the methodology is provided with a real example. --

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