A diagnostic model and several new diagnostic statistics are proposed for testing for varying dispersion in exponential family nonlinear models. A score statistic and an adjusted score statistic based on Cox and Reid (1987, J. Roy. Statist. Soc. Ser. B, 55, 467-471) are derived in normal, inverse Gaussian, and gamma nonlinear models. An adjusted likelihood ratio statistic is also given for normal and inverse Gaussian nonlinear models. The results of simulation studies are presented, which show that the adjusted tests keep their sizes better and are more powerful than the ordinary tests.
机构:
Southeast Univ, Dept Math, Nanjing 210096, Peoples R ChinaSoutheast Univ, Dept Math, Nanjing 210096, Peoples R China
Lin, Jin-Guan
Li, Yong
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Sun Yat Sen Univ, Dept Finance & Investment, Guangzhou 510075, Guangdong, Peoples R ChinaSoutheast Univ, Dept Math, Nanjing 210096, Peoples R China