A Multiple Imputation Approach to Linear Regression with Clustered Censored Data

Weextend Wei and Tanner's (1991) multiple imputation approach insemi-parametric linear regression for univariate censored datato clustered censored data. The main idea is to iterate the followingtwo steps: 1) using the data augmentation to impute for censoredfailure times; 2) fitting a linear model with imputed completedata, which takes into consideration of clustering among failuretimes. In particular, we propose using the generalized estimatingequations (GEE) or a linear mixed-effects model to implementthe second step. Through simulation studies our proposal comparesfavorably to the independence approach (Lee et al., 1993), whichignores the within-cluster correlation in estimating the regressioncoefficient. Our proposal is easy to implement by using existingsoftwares.     

Smoothing for discrete-valued time series

We deal with smoothed estimators for conditional probability functions of discrete-valued time series { Y_t } under two different settings. When the conditional distribution of Y_t given its lagged values falls in a parametric family and depends on exogenous random variables, a smoothed maximum (partial) likelihood estimator for the unknown parameter is proposed. While there is no prior information on the distribution, various nonparametric estimation methods have been compared and the adjusted Nadaraya–Watson estimator stands out as it shares the advantages of both Nadaraya–Watson and local linear regression estimators. The asymptotic normality of the estimators proposed has been established in the manner of sparse asymptotics, which shows that the smoothed methods proposed outperform their conventional, unsmoothed, parametric counterparts under very mild conditions. Simulation results lend further support to this assertion. Finally, the new method is illustrated via a real data set concerning the relationship between the number of daily hospital admissions and the levels of pollutants in Hong Kong in 1994–1995. An ad hoc model selection procedure based on a local Akaike information criterion is proposed to select the significant pollutant indices.     

交易延迟与机构投资者交易策略研究

对于机构投资者而言,出清具有一定规模的证券时,其提交指令的行为将对证券价格造成冲击形成交易成本,之后指令执行延迟也造成交易成本。文章以既定风险厌恶的机构投资者为研究对象,探讨其在交易延迟下的最优指令提交策略。经研究表明:交易延迟下最优指令提交策略受风险态度、证券收益、证券价格的波动性、市场的流动性与深度以及瞬时冲击程度等参数影响,不同市场的情况要求机构投资者调整策略,改变指令提交过程。     

人格特质对授权感知的调节效应研究

一、引言 传统的授权理论认为,授权就是将权利分派给其他人以完成特定活动的过程,也就是说,把决策权从组织的一个层级移交到另一个层级(Astly,1984)[1].现代授权理论则认为,授权的本质在于尽可能释放员工的知识、经验和动力,增加员工自我效能感,消除员工"无权"的感觉(Arad & Drasgow ,1994;Conger & Kanungo,1988;Spreitzer,1996).正如Lee和Koh(2001)指出的,授权实际上有两个完全不同的方面,一方面是主管给下属授权的"行为",另一方面是下属感知这种授权行为的"心理状态",即授权感知.     

循环经济的理论与实践：近期讨论综述

自从1966年美国经济学家鲍尔丁提出循环式经济的概念以来,循环经济理念逐渐在世界范围内传播开来。近年来,我国在经济发展过程中遇到了资源和环境的双重瓶颈,循环经济逐渐被国人所认同,而后更是被提到了战略的高度。与逐步升温的循环经济热相对应,国内学者对于循环经济问题的讨论也进行得如火如荼。本文拟把最近几年以来在国内公开发表的相关文献做一综述并提出未来的研究方向。一、循环经济的内涵总体上来说,国内学者基本上都是基于以下两方面阐述了循环经济的内涵:1.循环经济是生态经济。曲格平(2003)认为,循环经济就是一种与环境和谐的经…     

基于协整方法和VAR模型的中国行政管理成本变动分析

一、文献回顾:行政管理成本变动的原因长期以来,国家的行政管理成本问题一直受到学术界的关注。单从现有的定量研究成果看,对于行政管理成本变动的原因,大多数研究者从经济增长角度进行研究,但对于它如何影响政府规模,有两种截然不同的观点:一种观点认为,随着经济的发展,保证行使国家职能的公共支出要不断增加,政府消费性支出占国民所得的比重也不断上升。这就是所谓的“公共支出不断增长法则”,或称“政府活动扩张法则”,又称“瓦格纳法则”。20世纪以来,一些经济学家利用现代计量经济方法进行的研究也证实了这一“法则”。例如,Rubbinson…     

Effects of unmeasured heterogeneity in the linear transformation model for censored data

We investigate the effect of unobserved heterogeneity in the context of the linear transformation model for censored survival data in the clinical trials setting. The unobserved heterogeneity is represented by a frailty term, with unknown distribution, in the linear transformation model. The bias of the estimate under the assumption of no unobserved heterogeneity when it truly is present is obtained. We also derive the asymptotic relative efficiency of the estimate of treatment effect under the incorrect assumption of no unobserved heterogeneity. Additionally we investigate the loss of power for clinical trials that are designed assuming the model without frailty when, in fact, the model with frailty is true. Numerical studies under a proportional odds model show that the loss of efficiency and the loss of power can be substantial when the heterogeneity, as embodied by a frailty, is ignored. An erratum to this article can be found at     

从制度和文化层面看现代企业集团的经济性

现代企业集团是世界经济发展过程中的一个普遍现象,它对于推动社会生产力的发展具有重要意义。本文首先从企业集团的特征入手,分析了现代企业集团的实质;其次,从制度和文化两个层面,分析了现代企业集团的组织经济性和名牌经济性     

CeO2／蛇纹石体系对饮用水的脱氟行为研究

本文探讨了利用均相沉淀法制备的二氧化铈的脱氟行为,并利用蛇纹石作为载体,对CeO2/蛇纹石体系的除氟行为及最佳条件进行了进一步的研究,结果表明：均相沉淀法得到的二氧化铈除氟效率高,除氟容量可达11.76mg/g。以二氧化铈;蛇纹石为1：10的混合体系的除氟容量大大高于其他方法处理过的蛇纹石体系,其附近氟容量达到0.568mg/g。     

注重素质培养,实现教育实习的目的

面对实习学校设备参差不齐,指导教师素质有高有低,实习学生来源、民族、性别比例不均的状况,我校教育实习相应地采取了城乡结合式、基地式等多种形式.在实习中,通过准备、实习、总结三个阶段,加强学生教风、教态、仪表、行为、着装、语言和板书的专门素质教育,以期达到教育实习的目的.