Centered Partition Processes: Informative Priors for Clustering (with Discussion)

There is a very rich literature proposing Bayesian approaches for clustering starting with a prior probability distribution on partitions. Most approaches assume exchangeability, leading to simple representations in terms of Exchangeable Partition Probability Functions (EPPF). Gibbs-type priors encompass a broad class of such cases, including Dirichlet and Pitman-Yor processes. Even though there have been some proposals to relax the exchangeability assumption, allowing covariate-dependence and partial exchangeability, limited consideration has been given on how to include concrete prior knowledge on the partition. For example, we are motivated by an epidemiological application, in which we wish to cluster birth defects into groups and we have prior knowledge of an initial clustering provided by experts. As a general approach for including such prior knowledge, we propose a Centered Partition (CP) process that modifies the EPPF to favor partitions close to an initial one. Some properties of the CP prior are described, a general algorithm for posterior computation is developed, and we illustrate the methodology through simulation examples and an application to the motivating epidemiology study of birth defects

A Foxp2 Mutation Implicated in Human Speech Deficits Alters Sequencing of Ultrasonic Vocalizations in Adult Male Mice

Contains fulltext : 161830.pdf (publisher's version ) (Open Access

The local Dirichlet process

Dependent Dirichlet process, Blocked Gibbs sampler, Mixture model, Non-parametric Bayes, Stick-breaking representation,

‘We thought if it’s going to take two years then we need to start that now’: Age, infertility risk and the timing of pregnancy in older first-time mothers

Over the past few decades, the number of women having their first babies over the age of thirty-five in most developed societies has steadily increased. Concerns have been raised over this trend amidst warnings of both the increased risk of fertility problems and health risks to mother and child. Despite this, research into the timing of pregnancy in the context of decreasing fertility has been somewhat neglected, with research typically framed in biomedical rather than social terms. However, this area merits closer attention given the contradictory nature of societal messages that simultaneously encourage women to pursue careers and enhance lifestyle, whilst warning of ‘risks’ of infertility and problems in ‘delaying’ motherhood. This article is based on a small-scale qualitative study that uses data drawn from eleven in-depth interviews with ‘older mothers’ about their transition to motherhood. The data was thematically analysed. We found that the women drew upon risk discourses around decreasing fertility and advancing maternal age, and that these discourses impacted on their decisions about the timing of their pregnancies. Some mothers felt that they started trying to conceive at ‘non-ideal’ times, owing to expectations they held about decreasing fertility. We suggest that the impact of contradictory societal messages around the timing of motherhood need to be more clearly considered for their potential effects on the timing of pregnancy and note how this topic brings the personal, and, by implication, the societal, into conflict with the (narrated) biological