Regularized proportional odds models

The proportional odds model (POM) is commonly used in regression analysis to predict the outcome for an ordinal response variable. The maximum likelihood estimation (MLE) approach is typically used to obtain the parameter estimates. The likelihood estimates do not exist when the number of parameters, p, is greater than the number of observations n. The MLE also does not exist if there are no overlapping observations in the data. In a situation where the number of parameters is less than the sample size but p is approaching to n, the likelihood estimates may not exist, and if they exist they may have quite large standard errors. An estimation method is proposed to address the last two issues, i.e. complete separation and the case when p approaches n, but not the case when p>n. The proposed method does not use any penalty term but uses pseudo-observations to regularize the observed responses by downgrading their effect so that they become close to the underlying probabilities. The estimates can be computed easily with all commonly used statistical packages supporting the fitting of POMs with weights. Estimates are compared with MLE in a simulation study and an application to the real data.     

CEO duality and firm performance: The moderating roles of other executives and blockholding outside directors

This study examines how the effect of CEO duality on firm performance is affected by two internal governance forces – namely other executives in the top management team and blockholding outside directors. Results based on a longitudinal dataset from the U.S. computer industry were consistent with my hypotheses. Specifically, I found that the effect of CEO duality was negative when the CEO had dominant power relative to other executives and when the board had a blockholding outside director, but was nonsignificant otherwise. This study enriches our understanding of the effect of CEO duality, and helps reinforce the call for the nonduality structure as the default choice and put the burden of proof on those who wish to justify otherwise on special grounds.     

基于活动方法的瓶颈模型与拥挤收费问题研究

Vickrey提出的基于出行的瓶颈模型以出行作为分析单位,没有考虑出行与活动之间的相互关联.本文对Vickrey的瓶颈模型进行了拓展,提出了基于活动的瓶颈模型来研究通勤者早晨上班出发时间决策问题,模型考虑了通勤者对出行负效用与活动效用之间的权衡.在基于活动的瓶颈模型的基础上,分别研究了常数和线性边际活动效用下瓶颈动态拥挤收费和阶梯收费问题,并与传统的瓶颈模型的解进行比较.结果表明,当活动的边际效用为线性函数时,瓶颈处最优动态收费曲线不再呈分段线性关系,而是分段二次曲线;与基于活动的瓶颈模型相比,传统的基于出行的瓶颈模型将高估瓶颈处的排队延误、阶梯收费水平,以及早高峰的开始和结束时间;基于出行的瓶颈模型和常数边际活动效用下的瓶颈模型导致的最优阶梯收费是最优动态收费最大值的一半,并且刚好消除瓶颈处排队延误的一半;与线性边际活动效用下的瓶颈模型相比较,两者低估了阶梯收费能消除的瓶颈排队,从而低估了阶梯收费的效率.     

Link-tracing sampling with an initial sequential sample of sites: Estimating the size of a hidden human population

We proposed a modification to the variant of link-tracing sampling suggested by Félix-Medina and Thompson [M.H. Félix-Medina, S.K. Thompson, Combining cluster sampling and link-tracing sampling to estimate the size of hidden populations, Journal of Official Statistics 20 (2004) 19–38] that allows the researcher to have certain control of the final sample size, precision of the estimates or other characteristics of the sample that the researcher is interested in controlling. We achieve this goal by selecting an initial sequential sample of sites instead of an initial simple random sample of sites as those authors suggested. We estimate the population size by means of the maximum likelihood estimators suggested by the above-mentioned authors or by the Bayesian estimators proposed by Félix-Medina and Monjardin [M.H. Félix-Medina, P.E. Monjardin, Combining link-tracing sampling and cluster sampling to estimate the size of hidden populations: A Bayesian-assisted approach, Survey Methodology 32 (2006) 187–195]. Variances are estimated by means of jackknife and bootstrap estimators as well as by the delta estimators proposed in the two above-mentioned papers. Interval estimates of the population size are obtained by means of Wald and bootstrap confidence intervals. The results of an exploratory simulation study indicate good performance of the proposed sampling strategy.     

超越“范式”：国际问题研究的路径探微

当代国际政治理论的发展演变表现出一种对国际政治现象进行多重视角、多种层次研究的趋势，它给予人们的一个重要启示就是，没有一种能够解释一切的理论。但反过来说，不同的理论针对不同的对象也具有各不相同的解释力。我们必须认识到任何单一的理论都不可能解释国家对外行为的全部复杂性，必须提出一种综合的分析框架，结合现实主义、自由主义和建构主义各自精到的阐述，从历史、经济、政治、文化的视角来进行阐述和分析。     

大学英语交际教学法新思考

自20世纪70年代以来，交际教学法已成为国内外语言教学颇受青睐的教学方法。交际教学法主张以具体的交际功能项目为线索来安排教学内容，而不是以语言形式来安排内容，激发学生的学习兴趣，提高了语言运用能力。然而，交际教学法的教材增加了语法学习的困难，为此，同一功能表达形式多样对测试的不利及对教师专业培训要求更高等问题，足以引起英语一线教学同仁们的新思考。     

解读“80后”大学生道德认识矛盾性提高德育效益

为了探索新形势下实施德育的有效途径,提高德育效益,笔者针对“80后”大学生的道德认识进行了问卷抽查。在对调查结果进行综合分析的基础上,认识到：“80后”大学生的道德认识具有矛盾性,并分析了道德认识矛盾性的原因,重点从三个层面提出提高德育效益的途径：第一,社会层面,重构社会高层价值体系;第二,学校层面,要树立全员育人的大德育观念,内容要具有可接受性,方法上要加强情境性教育、体验性教育;第三,大学生要注重自我教育。     

Continuity of f-projections and applications to the iterative proportional fitting procedure*

This paper proves continuity of f-projections and the continuous dependence of the limit matrix of the iterative proportional fitting procedure (IPF procedure) on the given matrix as well as the given marginals under certain regularity constraints. For finite spaces, the concept of f-projections of finite measures on a compact and convex set is introduced and continuity of f-projections is proven. This result is applied to the IPF procedure. Given a nonnegative matrix as well as row and column marginals the IPF procedure generates a sequence of matrices, called the IPF sequence, by alternately fitting rows and columns to match their respective marginals. The procedure is equivalent to cyclic f-projections. If the IPF sequence converges, the application of the continuity of f-projections yields the continuous dependence of the limit matrix on the given matrix. By generalized convex programming and under some constraints, it is shown that the limit matrix of the IPF sequence continuously depends not only on the given matrix but also on the marginals.     

Home-Based Palliative Care Study

Abstract

Purpose: To examine differences in site of death and costs of services by primary diagnosis for patients receiving home-based palliative care as compared to usual care at the end of life verity of illness, service use, and site of death.

Design and Methods: A nonequivalent group design was employed with 298 terminally ill patients diagnosed with cancer, CHF, or COPD enrolled. The treatment group received an interdisciplinary home-based palliative care program and the comparison group received usual Kaiser Permanente services. Data collected included patient demographics, se-

Results: Among all diseases, patients enrolled in palliative care were more likely to die at home. Enrollment in palliative care was significant associated with cost reductions for patients with cancer, COPD, and CHF. No significant difference was found between diagnostic groups in terms of magnitude of cost savings.

Implications: Provision of interdisciplinary home-based palliative care at end of life can effectively increase the likelihood of dying at home for patients with CHF, COPD, and cancer while realizing significant COSt savings.