A robust multivariate measurement error model with skew-normal/independent distributions and Bayesian MCMC implementation

Skew-normal/independent distributions are a class of asymmetric thick-tailed distributions that include the skew-normal distribution as a special case. In this paper, we explore the use of Markov Chain Monte Carlo (MCMC) methods to develop a Bayesian analysis in multivariate measurement errors models. We propose the use of skew-normal/independent distributions to model the unobserved value of the covariates (latent variable) and symmetric normal/independent distributions for the random errors term, providing an appealing robust alternative to the usual symmetric process in multivariate measurement errors models. Among the distributions that belong to this class of distributions, we examine univariate and multivariate versions of the skew-normal, skew-t, skew-slash and skew-contaminated normal distributions. The results and methods are applied to a real data set.     

推进区域自主创新联盟发展研究——基于湖南十四个市州的调研分析

通过对湖南区域创新能力现状、湖南区域产业发展现状进行分析,对湖南区域技术创新联盟的组建情况进行调查统计后其认为,湖南区域自主创新联盟发展应在战略性新兴产业和区域主导产业内重点推进。在战略性新兴产业内,应该在高端工程机械装备、轨道交通装备等领域内重点推进。各市州也应该根据各自主导产业或优势产业情况,在相应的领域内重点推进。     

Leaving an Institution in Flanders (Belgium): A Road to Homelessness?

People living in an institution will leave this residential context one day and have to proceed to a stable independent way of living. This transition is not without difficulties as it turns out this socially vulnerable group runs an increased risk of becoming homeless. Research in Flanders (Belgium) has shown that a considerable share of the homeless population has previously stayed in an institutional setting, mostly in youth care (48.7%), psychiatric (34.4%) and penitentiary (33.1%) institutions. Moreover, the share of homeless people with a history in one of these institutions has increased in the past decades. Institution leavers, face at least three obstacles to a stable housing situation in Flanders: a lack of affordable housing, a lack of access to (non-residential) social assistance and personal difficulties in coping with living independently. Yet, there are several programs that support institution leavers and prepare them for the transition to an independent living situation and legal developments that strengthen their position in society and on the housing market. In this paper, we explore these initiatives and developments in three case studies (Antwerp, Ghent and Leuven). Based on in-depth interviews with “street-level bureaucrats” who work in these institutions (youth care, psychiatric and penitentiary settings), social support services and social housing organizations, we reconstruct the pathways of institution leavers to the housing market, the support they receive and the experienced difficulties.     

Evaluation of Research Ethics Committees: Criteria for the Ethical Quality of the Review Process

Repeatedly, adequacy, performance and quality of Ethics Committees that oversee medical research trials are being discussed. Although they play a crucial role in reviewing medical research and protecting human subjects, it is far from clear to what degree they fulfill the task they have been assigned to. This eventuates in the call for an evaluation of their activity and, in some places, led to the establishment of accreditation schemes. At the same time, IRBs have become subject of detailed legislation in the process of the ongoing global juridification of medical research. Unsurprisingly, there is a tendency to understand the evaluation of RECs as a question of controlling their legal compliance. This paper discusses the need for a quality evaluation of IRBs from an ethical point of view and, by systematically reviewing the major ethical guidelines for IRBs, proposes a system of criteria that should orientate any evaluation of IRBs.     

Assessing Effects on Long-term Survival after Early Termination of Randomized Trials

In this paper we present an approach to using historical control data to augment information from a randomized controlled clinical trial, when it is not possible to continue the control regimen to obtain the most reliable and valid assessment of long term treatment effects. Using an adjustment procedure to the historical control data, we investigate a method of estimating the long term survival function for the clinical trial control group and for evaluating the long term treatment effect. The suggested method is simple to interpret, and particularly motivated in clinical trial settings when ethical considerations preclude the long term follow-up of placebo controls. A simulation study reveals that the bias in parameter estimates that arises in the setting of group sequential monitoring will be attenuated when long term historical control information is used in the proposed manner. Data from the first and second National Wilms' Tumor studies are used to illustrate the method.     

Optimal use of two auxiliary variables in double sampling

Double sampling scheme is used when cheap auxiliary variables may be measured to improve the estimation of a finite population parameter. Several estimators for population mean, ratio of means and variance are available, when two dependent samples are drawn. However, there are few proposals for the case of independent samples. In this paper both cases of dependent and independent samples are dealt with. A general approach for estimating a finite population parameter is given, showing that all the proposed estimators are particular cases of the same general class. The minimum variance bound for any estimator in this class is provided (at the first order of approximation). Furthermore, an optimal estimator which reaches this minimum is found.     

Sequential experimental design and response optimisation

We consider the situation where one wants to maximise a functionf(θ,x) with respect tox, with θ unknown and estimated from observationsy _k . This may correspond to the case of a regression model, where one observesy _k =f(θ,x _k )+ε _k , with ε _k some random error, or to the Bernoulli case wherey _k ∈{0, 1}, with Pr[y _k =1|θ,x _k |=f(θ,x _k ). Special attention is given to sequences given by , with an estimated value of θ obtained from (x₁, y₁),...,(x _k ,y _k ) andd _k (x) a penalty for poor estimation. Approximately optimal rules are suggested in the linear regression case with a finite horizon, where one wants to maximize ∑ _i=1 ^N w _i f(θ, x _i ) with {w _i } a weighting sequence. Various examples are presented, with a comparison with a Polya urn design and an up-and-down method for a binary response problem.     

"结构-发展"自我理论与自主学习关系刍议

“结构-发展”理论的核心思想是“意义采择”,认为自我是意义采择的结果。其理论对我们全面认识自主学习的 内涵,探讨自主学习与个性发展的关系提供了有益的启示。     

民办本科大学生信仰观问题探究——以浙江海洋学院东海科学技术学院为例

大学生信仰观现状是目前社会和高校十分关注的教育问题,是大学生思想政治教育的核心内容,在大学生的成长过程中具有重要的作用。树立科学正确的信仰观对今后的人生道路具有重要意义。本文以浙江海洋学院东海科学技术学院为例,基于实地取证与调查的最新数据,以此为据研究民办本科院校学生的信仰观现状及存在的问题并提出解决方法。