Comparison of four growth curve models in Angus cow : an application of Bayesian nonlinear mixed model

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Comparison of four growth curve models in Angus cow : an application of Bayesian nonlinear mixed model

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Title: Comparison of four growth curve models in Angus cow : an application of Bayesian nonlinear mixed model
Author: Qin, Qing, master of science in statistics
Abstract: The purpose of this study was to compare 4 growth curve functions (Brody, Logistic, Gompertz, and Von Bertalanffy) in describing the weight change across age in Angus cow. A total of 1,705 weight-age records from birth to at least 3-year of age from 171 cows were collected. All the growth models were fitted as a nonlinear mixed model using NLMIXED procedure in SAS9.2 (REML Approach) and MCMC method through WinBUGS (Bayesian Approach). The goodness of fit of these four models was compared in terms of AIC, BIC, and DIC. The results show that the Gompertz model fitted the data best under REML Approach while the Brody model appeared to be the best model under Bayesian Approach. The Bayesian Approach provided more flexibility in setting up the mixed model and more reasonable estimates for all the growth models compared to the REML Approach. These results show some advantages of Bayesian nonlinear mixed modeling.
Department: Statistics
Subject: Bayesian mixed model Growth curves WinBUGS
URI: http://hdl.handle.net/2152/ETD-UT-2012-05-5299
Date: 2012-05

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