Finite mixture models for proportions

Brooks, Stephen P. and Morgan, Byron J. T. and Ridout, Martin S. and Pack, S.E. (1997) Finite mixture models for proportions. Biometrics, 53 (3). pp. 1097-1115. ISSN 0006-341X. (The full text of this publication is not currently available from this repository. You may be able to access a copy if URLs are provided)

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Six data sets recording fetal control mortality in mouse litters are presented. The data are clearly overdispersed, and a standard approach would be to describe the data by means of a beta-binomial model or to use quasi-likelihood methods. For five of the examples, we show that the beta-binomial model provides a reasonable description but that the fit can be significantly improved by using a mixture of a beta-binomial model with a binomial distribution. This mixture provides two alternative solutions, in one of which the binomial component indicates a high probability of death but is selected infrequently; this accounts for outlying litters with high mortality. The influence of the outliers on the beta-binomial fits is also demonstrated. The location and nature of the two main maxima to the likelihood are investigated through profile log-likelihoods. Comparisons are made with the performance of finite mixtures of binomial distributions.

Item Type: Article
Depositing User: T. Nasir
Date Deposited: 28 Oct 2009 18:19
Last Modified: 18 Jun 2014 09:53
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