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 available from this repository)
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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.
|Depositing User:||T. Nasir|
|Date Deposited:||28 Oct 2009 18:19|
|Last Modified:||18 Jun 2014 09:53|
|Resource URI:||http://kar.kent.ac.uk/id/eprint/18310 (The current URI for this page, for reference purposes)|