Bayesian partial likelihood approach for tied observations

The Bayesian analysis based on the partial likelihood for Cox's proportional hazards model is frequently used because of its simplicity. The Bayesian partial likelihood approach is often justified by showing that it approximates the full Bayesian posterior of the regression coefficients with a diffuse prior on the baseline hazard function. This, however, may not be appropriate when ties exist among uncensored observations. In that case, the full Bayesian and Bayesian partial likelihood posteriors can be much different. In this paper, we propose a new Bayesian partial likelihood approach for many tied observations and justify its use.     

Nonparametric and semiparametric estimation of the three way receiver operating characteristic surface

In many situations the diagnostic decision is not limited to a binary choice. Binary statistical tools such as receiver operating characteristic (ROC) curve and area under the ROC curve (AUC) need to be expanded to address three-category classification problem. Previous authors have suggest various ways to model the extension of AUC but not the ROC surface. Only simple parametric approaches are proposed for modeling the ROC measure under the assumption that test results all follow normal distributions. We study the estimation methods of three-dimensional ROC surfaces with nonparametric and semiparametric estimators. Asymptotical results are provided as a basis for statistical inference. Simulation studies are performed to assess the validity of our proposed methods in finite samples. We consider an Alzheimer's disease example from a clinical study in the US as an illustration. The nonparametric and semiparametric modelling approaches for the three way ROC analysis can be readily generalized to diagnostic problems with more than three classes.     

Copula-based regression models: A survey

In this review paper we collect several results about copula-based models, especially concerning regression models, by focusing on some insurance applications.     

Forecasting obesity trends in England

Summary.  Forecasts of trends in obesity in England for 2010 are produced by treating the available data, which contain the proportions of the population, categorized by age and sex, falling into different body mass index ranges, as compositional data sets, so that the implicit simplex restrictions are automatically satisfied. Forecasts are calculated by using linear trend models for the log-ratio transformations and are accompanied by prediction regions. The advantages of treating data on proportions compositionally are emphasized and compared with forecasts that have been obtained by ignoring this restriction.     

Using relative utility curves to evaluate risk prediction

Summary.  Because many medical decisions are based on risk prediction models that are constructed from medical history and results of tests, the evaluation of these prediction models is important. This paper makes five contributions to this evaluation: the relative utility curve which gauges the potential for better prediction in terms of utilities, without the need for a reference level for one utility, while providing a sensitivity analysis for misspecification of utilities, the relevant region, which is the set of values of prediction performance that are consistent with the recommended treatment status in the absence of prediction, the test threshold, which is the minimum number of tests that would be traded for a true positive prediction in order for the expected utility to be non-negative, the evaluation of two-stage predictions that reduce test costs and connections between various measures of performance of prediction. An application involving the risk of cardiovascular disease is discussed.     

Using Bayesian graphical models to model biases in observational studies and to combine multiple sources of data: application to low birth weight and water disinfection by-products

Summary.  Data in the social, behavioural and health sciences frequently come from observational studies instead of controlled experiments. In addition to random errors, observational data typically contain additional sources of uncertainty such as missing values, unmeasured confounders and selection biases. Also, the research question is often different from that which a particular source of data was designed to answer, and so not all relevant variables are measured. As a result, multiple sources of data are often necessary to identify the biases and to inform about different aspects of the research question. Bayesian graphical models provide a coherent way to connect a series of local submodels, based on different data sets, into a global unified analysis. We present a unified modelling framework that will account for multiple biases simultaneously and give more accurate parameter estimates than standard approaches. We illustrate our approach by analysing data from a study of water disinfection by-products and adverse birth outcomes in the UK.     

青岛地区农民生活消费特征及影响因素分析

改革开放以来,青岛地区农民的物质和精神文化消费观念变化显著,交通信息费增长迅速,医疗保健支出增加及突出性消费显著。农民收入增长缓慢,消费环境不健全,社会保障体系不完善是影响农民生活消费特征变化的主要因素,要进一步引导农民科学消费可从切实增加农民收入,完善社会保障体系,加强农村文化建设等几个方面着手。     

功能语篇分析在高职大学英语阅读教学中的运用

本文认为功能语篇衔接理论的运用,有助于提高教学质量和学习成效。     

Organizational ecology of immigrant employment and organizational buffer zones: Who leaves first when the organization gets into trouble?

Using data from the German social insurance system immigrant employment in organizational buffer zones will be investigated from an organizational ecology perspective. Theories in organization and labor market research predict higher exit rates of employees holding jobs in buffer zones. These buffer zones protect organizations from unfavorable environmental turbulences. Consequently, analyzing the impact of buffer zone employment on job stability of immigrants requires a fully dynamic approach, which goes beyond a mere identification of generally increased turnover rates of immigrants.In the first step, determinants of organizational dissolution rates will be estimated. In order to obtain a dynamic measurement of unfavorable environmental conditions, the model includes both organizational and time-varying environmental characteristics of organizational populations. This will be done by using a three-level mixed-effects hazard model controlling for observed and unobserved environmental characteristics. In the second step, dissolution rates predicted in the first step will be used as an explanatory variable. These rates indicate the degree of enactment of the flexible buffer zone. It will be shown that immigrants have indeed higher turnover rates, but they tend to remain longer in their organizations when environmental conditions deteriorate—and they are not those who leave first when the organization gets into trouble.     

行刑一体化与刑罚执行权的新配置

尽管行刑是刑罚运用过程的最后环节,但是,行刑效果如何则直接关系到刑罚目的能否最终实现。科学合理地配置刑罚执行权将有助于行刑效率的提高与刑罚运行机制的完备。通过对当代中国刑罚执行权的现实考察,不难发现,中国现行刑罚执行权配置并不科学合理,存在着行刑权过于分散、相互之间彼此抵牾之处,这严重地影响了刑罚功能的发挥。因此,树立行刑一体化的理念,科学地配置刑罚执行权,乃是中国刑法理论界与实务界共同努力的方向和目标。