Influence diagnostics for polyhazard models in the presence of covariates |
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Authors: | Juliana B Fachini Edwin M M Ortega Francisco Louzada-Neto |
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Institution: | 1.ESALQ,Universdade de S?o Paulo,Piracicaba,Brazil;2.Departamento de Ciências Exatas,USP,Piracicaba,Brazil;3.DEs,Universidade Federal S?o Carlos,S?o Carlos,Brazil |
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Abstract: | In this paper, we present various diagnostic methods for polyhazard models. Polyhazard models are a flexible family for fitting
lifetime data. Their main advantage over the single hazard models, such as the Weibull and the log-logistic models, is to
include a large amount of nonmonotone hazard shapes, as bathtub and multimodal curves. Some influence methods, such as the
local influence and total local influence of an individual are derived, analyzed and discussed. A discussion of the computation
of the likelihood displacement as well as the normal curvature in the local influence method are presented. Finally, an example
with real data is given for illustration. |
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Keywords: | Polyhazard model Poly-Weibull distribution Poly-log-logistic distribution Influence diagnostics Residual analysis |
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