A Method to Handle Zero Counts in the Multinomial Model

In the context of an objective Bayesian approach to the multinomial model, Dirichlet(a, …, a) priors with a < 1 have previously been shown to be inadequate in the presence of zero counts, suggesting that the uniform prior (a = 1) is the preferred candidate. In the presence of many zero counts, however, this prior may not be satisfactory either. A model selection approach is proposed, allowing for the possibility of zero parameters corresponding to zero count categories. This approach results in a posterior mixture of Dirichlet distributions and marginal mixtures of beta distributions, which seem to avoid the problems that potentially result from the various proposed Dirichlet priors, in particular in the context of extreme data with zero counts.     

Bayesian Estimation and Model Choice in Item Response Models

Item response models are essential tools for analyzing results from many educational and psychological tests. Such models are used to quantify the probability of correct response as a function of unobserved examinee ability and other parameters explaining the difficulty and the discriminatory power of the questions in the test. Some of these models also incorporate a threshold parameter for the probability of the correct response to account for the effect of guessing the correct answer in multiple choice type tests. In this article we consider fitting of such models using the Gibbs sampler. A data augmentation method to analyze a normal-ogive model incorporating a threshold guessing parameter is introduced and compared with a Metropolis-Hastings sampling method. The proposed method is an order of magnitude more efficient than the existing method. Another objective of this paper is to develop Bayesian model choice techniques for model discrimination. A predictive approach based on a variant of the Bayes factor is used and compared with another decision theoretic method which minimizes an expected loss function on the predictive space. A classical model choice technique based on a modified likelihood ratio test statistic is shown as one component of the second criterion. As a consequence the Bayesian methods proposed in this paper are contrasted with the classical approach based on the likelihood ratio test. Several examples are given to illustrate the methods.     

对我国高校社会工作专业人才培养的思考

2011年11月,中组部等18个部门和组织联合发布《关于加强社会工作专业人才队伍建设的意见》,充分说明国家对社会工作专业人才的高度重视,同时也进一步体现经济社会发展对社会工作专业人才的迫切需求。因此,高质量社会工作专业人才的培养已经成为高等学校的重大课题,本文从人才培养目标定位、服务面向、培养模式构建等三个重要方面切入,提出对我国高校社会工作专业人才培养的思考。     

A Comparative Study of Model-based Tests of Independence for Ordinal Data Using the Bootstrap

When analyzing categorical data using loglinear models in sparse contingency tables, asymptotic results may fail. In this paper the empirical properties of three commonly used asymptotic tests of independence, based on the uniform association model for ordinal data, are investigated by means of Monte Carlo simulation. Five different bootstrapped tests of independence are presented and compared to the asymptotic tests. The comparisons are made with respect to both size and power properties of the tests. Results indicate that the asymptotic tests have poor size control. The test based on the estimated association parameter is severely conservative and the two chi-squared tests (Pearson, likelihood-ratio) are both liberal. The bootstrap tests that either use a parametric assumption or are based on non-pivotal test statistics do not perform better than the asymptotic tests in all situations. The bootstrap tests that are based on approximately pivotal statistics provide both adjustment of size and enhancement of power. These tests are therefore recommended for use in situations similar to those included in the simulation study.     

嫩模现象：一种新兴青年文化

嫩模现象是个横空出世的新兴青年文化现象，亦是香港普及文化的重要一课。讨论嫩模现象的由来，以及在众声喧哗中隐含的各种文化政治，例如名人概念、青年概念、女性身体等，能检视社会主流论述对此等文化概念的意义转变和规训等。     

美国BIT范本的环境政策考量与变迁及其对中国的启示

美国从1981年启用第一个BIT范本,之后历经数次修订,形成不同版本。其中的环境保护条款从无到有、从简到繁,2012年版本对环境保护又有大力强化。虽然环境例外条款具有法律形态,但因其为缔约方保留环境规制的空间,没有消极影响,其他环境条款尤其专门环境条款则只具有政策形态,对缔约方只有倡导和督促作用,因而也不具有负面意义。基于此,对于中美BIT谈判,中国应该持有像实践WTO规则一样的心态,研究它、接受它,为投身国际实践走出第一步,为将来参与更大范围的规则制定做好准备。     

固定效应部分线性变系数面板模型的快速有效估计

本文将最小二乘支持向量机(LSSVM) 和二次推断函数法(QIF) 相结合，为个体内具有相关结构的固定效应部分线性变系数面板模型提供了一种新的快速估计方法；在一定的正则条件下，论证了参数估计量的渐近正态性和非参数估计量的收敛速度；采用Monte Carlo模拟考察了估计方法在有限样本下的表现并将估计技术应用于现实数据分析。该方法不仅保证了估计的有效性和统计推断力，而且程序运行速度得到较大幅度提升。     

“一带一路”战略与中国对阿拉伯国家出口潜力分析

欧美的贸易保护主义盛起之时转变外贸地理方向成为我国外贸的一项重要工作，恰逢中国率先提出的“一带一路”战略规划了东亚开放的地区主义，处于“一带一路”交汇处的阿拉伯国家便成为了我们天然的经贸合作伙伴，从而对阿拉伯国家的外贸出口呈现出愈来愈强的重要性。本文基于贸易引力模型，通过中国对阿拉伯国家联盟中的20个国家2001年～2010年间的货物贸易出口数据，测算了同各国间的贸易潜力，基于中国与阿拉伯国家间存在的较大贸易潜力提出了几点结论与启示。     

网络社区发现算法在流动表建模中的设计与应用

代际流动表可以统计子代与其父代社会地位配对数据的交互频数，反映了社会资源占有的优劣势在父子两代人之间的比较。对财富、阶级、特权等社会基本特征演变的实证考察，均依赖于代际流动表的量化分析。对数线性模型是流动表建模分析的基本工具，通过对列联表单元格频数进行拟合，可以识别流动表行分类与列分类之间的强弱交互效应，刻画父子社会地位间的交互结构。本文利用复杂网络社区发现算法分析父子社会地位的关联结构，针对简约对数线性模型拟合精度不够的问题，提出一种新的建模思路：利用社区发现算法对简约对数线性模型的残差列联表进行关联关系挖掘，将发现的社区效应作为附加参数约束引入原对数线性模型，以改善数据的拟合情况。由于该方法只在原简约对数线性模型中增加了一个参数约束，因此仍可以保证建模结果的简洁性及理论意义，同时社区效应补充了原对数线性模型对经验数据结构的解读。论文用此方法对来源于中国综合社会调查数据的经验代际职业流动表进行建模分析，较好地解释了子代职业阶层与父代职业阶层间的关联模式。     

西方儿童虐待成因的发展生态模型理论研究述评

发展生态模型是西方儿童虐待成因研究的重要理论框架,但国内对此缺少系统性介绍。该理论认为,儿童虐待产生自互动个体与嵌套生态系统层面间的交互影响,它主要以生态系统理论为理论基础,并以“生态整合模型”和“生态交互模型”为代表性理论模型。该理论具有重要的方法论意义,它可促使研究者突破单因素变量研究的窠臼,并转向多因素共构视角去理解儿童虐待成因;同时,也为儿童虐待治理实践提供了多因素和多层次的系统干预视角。该理论的出现丰富了儿童虐待研究者的理论想象力,可为我国家庭、学校等场域的儿童虐待和儿童保护研究和干预提供启示。