Browsing by Subject "Bayes factor"

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    Bayesian model selection approach to the one way analysis of variance under homoscedasticity
    (Springer, 2013-06) Cano, J. A.; Carazo, C.; Salmerón Martínez, Diego; Ciencias Sociosanitarias
    An objective Bayesian model selection procedure is proposed for the one way analysis of variance under homoscedasticity. Bayes factors for the usual default prior distributions are not well defined and thus Bayes factors for intrinsic priors are used instead. The intrinsic priors depend on a training sample which is typically a unique random vector. However, for the homoscedastic ANOVA it is not the case. Nevertheless, we are able to illustrate that the Bayes factors for the intrinsic priors are not sensitive to the minimal training sample chosen; furthermore, we propose an alternative pooled prior that yields similar Bayes factors. To compute these Bayes factors Bayesian computing methods are required when the sample sizes of the involved populations are large. Finally, a one to one relationship—which we call the calibration curve—between the posterior probability of the null hypothesis and the classical value is found, thus allowing comparisons between these two measures of evidence. The behavior of the calibration curve as a function of the sample size is studied and conclusions relating both procedures are stated.
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    Integral priors and constrained imaginary training samples for nested and non-nested Bayesian model Comparison
    (International Society for Bayesian Analysis, 2013-06) Cano JA; Salmerón D; Ciencias Sociosanitarias
    In Bayesian model selection when the prior information on the parameters of the models is vague default priors should be used. Unfortunately, these priors are usually improper yielding indeterminate Bayes factors that preclude the comparison of the models. To calibrate the initial default priors Cano et al. (2008) proposed integral priors as prior distributions for Bayesian model selection. These priors were defined as the solution of a system of two integral equations that under some general assumptions has a unique solution associated with a recurrent Markov chain. Later, in Cano et al. (2012b) integral priors were successfully applied in some situations where they are known and they are unique, being proper or not, and it was pointed out how to deal with other situations. Here, we present some new situations to illustrate how this new methodology works in the cases where we are not able to explicitly find the integral priors but we know they are proper and unique (one-sided testing for the exponential distribution) and in the cases where recurrence of the associated Markov chains is difficult to check. To deal with this latter scenario we impose a technical constraint on the imaginary training samples space that virtually implies the existence and the uniqueness of integral priors which are proper distributions. The improvement over other existing methodologies comes from the fact that this method is more automatic since we only need to simulate from the involved models and their posteriors to compute very well behaved Bayes factors.