Selection of suitable prior for the Bayesian mixture of a class of lifetime distributions under type-I censored datasets

This paper explores the study on mixture of a class of probability density functions under type-I censoring scheme. In this paper, we mold a heterogeneous population by means of a two-component mixture of the class of probability density functions. The parameters of the class of mixture density functions are estimated and compared using the Bayes estimates under the squared-error and precautionary loss functions. A censored mixture dataset is simulated by probabilistic mixing for the computational purpose considering particular case of the Maxwell distribution. Closed-form expressions for the Bayes estimators along with their posterior risks are derived for censored as well as complete samples. Some stimulating comparisons and properties of the estimates are presented here. A factual dataset has also been for illustration.     

Subjective elicitation of hyperparameters of a conjugate Dirichlet prior and the corresponding Bayes analysis

Abstract

The paper elicits subjectively the Dirichlet prior hyperparameters based on the realistic opinion collected from the experts. The procedure used for subjective elicitation considers several stages such as the choice of experts, formation of some relevant questions to be asked to the experts for getting their opinion, pooling of opinion, quantification of information and then the formation of exact prior distribution through quantile assessment based on an iterative procedure. The resulting prior distribution is used to provide the Bayes analysis assuming multinomial sampling plan. The results are illustrated by means of a data set involving two life style factors of gallbladder carcinoma patients. The results convey the message that matches closely with the opinion given by the medical experts.     

Prbposterior expected loss as a scoring rule for prior distributions

A scoring rule for evaluating the usefulness of an assessed prior distribution should reflect the purpose for which the distribution is to be used. In this paper we suppose that sample data is to become available and that the posterior distribution will be used to estimate some quantity under a quadratic loss function. The utility of a prior distribution is consequently determined by its preposterior expected quadratic loss. It is shown that this loss function has properties desirable in a scoring rule and formulae are derived for calculating the scores it gives in some common problems. Many scoring rules give a very poor score to any improper prior distribution but, in contrast, the scoring rule proposed here provides a meaningful measure for comparing the usefulness of assessed prior distributions and non-informative (improper) prior distributions. Results for making this comparison in various situations are also given.     

Bounding Poorly Characterized Risks: A Lung Cancer Example

For diseases with more than one risk factor, the sum of probabilistic estimates of the number of cases caused by each individual factor may exceed the total number of cases observed, especially when uncertainties about exposure and dose response for some risk factors are high. In this study, we outline a method of bounding the fraction of lung cancer fatalities not due to specific well-studied causes. Such information serves as a "reality check" for estimates of the impacts of the minor risk factors, and, as such, complements the traditional risk analysis. With lung cancer as our example, we allocate portions of the observed lung cancer mortality to known causes (such as smoking, residential radon, and asbestos fibers) and describe the uncertainty surrounding those estimates. The interactions among the risk factors are also quantified, to the extent possible. We then infer an upper bound on the residual mortality due to "other" causes, using a consistency constraint on the total number of deaths, the maximum uncertainty principle, and the mathematics originally developed of imprecise probabilities.     

Expert Judgment in Risk Analysis and Management: Process, Context, and Pitfalls

The regulation and management of hazardous industrial activities increasingly rely on formal expert judgment processes to provide wisdom in areas of science and technology where traditional "good science" is, in practice, unable to supply unambiguous "facts." Expert judgment has always played a significant, if often unrecognized, role in analysis; however, recent trends are to make it formal, explicit, and documented so it can be identified and reviewed by others. We propose four categories of expert judgment and present three case studies which illustrate some of the pitfalls commonly encountered in its use. We conclude that there will be an expanding policy role for formal expert judgment and that the openness, transparency, and documentation that it requires have implications for enhanced public involvement in scientific and technical affairs.     

Development of a Preliminary Framework for Informing the Risk Analysis and Risk Management of Nanoparticles

Decisions are often made even when there is uncertainty about the possible outcomes. However, methods for making decisions with uncertainty in the problem framework are scarce. Presently, safety assessment for a product containing engineered nano-scale particles is a very poorly structured problem. Many fields of study may inform the safety assessment of such particles (e.g., ultrafines, aerosols, debris from medical devices), but engineered nano-scale particles may present such unique properties that extrapolating from other types of studies may introduce, and not resolve, uncertainty. Some screening-level health effects studies conducted specifically on engineered nano-scale materials have been published and many more are underway. However, it is clear that the extent of research needed to fully and confidently understand the potential for health or environmental risk from engineered nano-scale particles may take years or even decades to complete. In spite of the great uncertainty, there is existing research and experience among researchers that can help to provide a taxonomy of particle properties, perhaps indicating a relative likelihood of risk, in order to prioritize nanoparticle risk research. To help structure this problem, a framework was developed from expert interviews of nanotechnology researchers. The analysis organizes the information as a system based on the risk assessment framework, in order to support the decision about safety. In the long term, this framework is designed to incorporate research results as they are generated, and therefore serve as a tool for estimating the potential for human health and environmental risk.     

谈体育课中的"激发教学"

本文论述了在体育课中应用"激发教学"的意义和途径.通过对"教材激发"和"教法激发"的阐释,努力探索出一条体育中"激发教学"的新路子,使体育课堂教学寓教于兴趣之中,增强体质,强化了教学效果,又陶冶了学生的情操.     

Elicitation of Subjective Probabilities when the Initial Endowment is Unobservable

In the framework of subjective expected utility theory we develop two distinct procedures for the elicitation of a person's subjective probabilities when the initial endowment is random and unobservable. Procedures of the first kind rely on the boundedness of the utility function to elicit the person's subjective probabilities directly. Procedures of the second kind infer the person's initial endowment from his choice behavior prior to the application of probability elicitation.     

‘The shops were only made for people who could walk’: impairment,barriers and autonomy in the mobility of adults with Cerebral Palsy in urban England

ABSTRACT

Based on research carried out with a group of adults with Cerebral Palsy in Birmingham, UK, we consider the complex inter-relationship between the accessibility of the urban environment for those with impaired gross motor skills, and the ability of these people to lead full and independent lives. Drawing on a framework that considers mobility as movement, meaning-making and political, we demonstrate the reality of differentiated mobility. For those with bodies that function outside the presumed operating parameters of the model subjects of urban design, mobility may be possible, but is often uncomfortable and even dangerous, with significant associated effects for impaired people’s autonomy. Our study details social and structural, or design, barriers to people’s mobility, demonstrating the inter-connection between individuals’ behaviour and urban design in a manner that questions a clear distinction between the two. We draw upon the notions of emotional work and a commoning approach to mobility in suggesting that further investment in urban accessibility is squarely an issue of social justice.     

精简教材内容 注重教学方法 提高教学质量--浅析《道路勘测设计》课程教学改革

针对目前《道路勘测设计》课程内容多学时少这一主要矛盾,提出了以精简教材内容、注重教学方法、提高教学质量为主的课程教学改革方案。特别强调了应加强启发式教学和学生自学,以求锻炼学生的创造性思维,逐步培养学生独立思考问题和分析问题的能力,亦即注重对学生智能和素质的培养。