Location-scale mixed models and goodness-of-fit assessment applied to insect ecology |
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Authors: | R A Moral J Hinde E M M Ortega C G B Demtrio W A C Godoy |
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Institution: | aDepartment of Mathematics and Statistics, Maynooth University, Maynooth, Ireland;bSchool of Mathematics, Statistics, and Applied Mathematics, NUI Galway, Galway, Ireland;cDepartment of Exact Sciences, ESALQ-USP, Piracicaba, Brazil;dDepartment of Entomology and Acarology, ESALQ-USP, Piracicaba, Brazil |
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Abstract: | Survival models have been extensively used to analyse time-until-event data. There is a range of extended models that incorporate different aspects, such as overdispersion/frailty, mixtures, and flexible response functions through semi-parametric models. In this work, we show how a useful tool to assess goodness-of-fit, the half-normal plot of residuals with a simulated envelope, implemented in the hnp package in R, can be used on a location-scale modelling context. We fitted a range of survival models to time-until-event data, where the event was an insect predator attacking a larva in a biological control experiment. We started with the Weibull model and then fitted the exponentiated-Weibull location-scale model with regressors both for the location and scale parameters. We performed variable selection for each model and, by producing half-normal plots with simulated envelopes for the deviance residuals of the model fits, we found that the exponentiated-Weibull fitted the data better. We then included a random effect in the exponentiated-Weibull model to accommodate correlated observations. Finally, we discuss possible implications of the results found in the case study. |
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Keywords: | Biological control exponentiated models half-normal plots with simulation envelopes location-scale modelling mixed survival models |
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