Backfitting Random Varying-Coefficient Models with Time-Dependent Smoothing Covariates

Abstract.  In this paper, we propose a random varying-coefficient model for longitudinal data. This model is different from the standard varying-coefficient model in the sense that the time-varying coefficients are assumed to be subject-specific, and can be considered as realizations of stochastic processes. This modelling strategy allows us to employ powerful mixed-effects modelling techniques to efficiently incorporate the within-subject and between-subject variations in the estimators of time-varying coefficients. Thus, the subject-specific feature of longitudinal data is effectively considered in the proposed model. A backfitting algorithm is proposed to estimate the coefficient functions. Simulation studies show that the proposed estimation methods are more efficient in finite-sample performance compared with the standard local least squares method. An application to an AIDS clinical study is presented to illustrate the proposed methodologies.     

Wilcoxon–Mann–Whitney test for stratified samples and Efron's paradox dice

Two-treatment multi-center clinical trials are the most common type of clinical trials in practice. The aim of this paper is to discuss a curious property of certain standard nonparametric procedures used in the analysis of such clinical trials. Different analyses of a simulated data example are presented, which lead to contrasting and surprising results. The source of the potentially misleading outcome is then explored while relating the simulated data with the concept of Efron's paradox dice and the notion of nontransitivity. With the root of the problem established, an alternate nonparametric method from the literature is shown to address the problem. Finally, pointing out an interpretational concern of using the alternate procedure, a modification to this procedure is also suggested and corresponding theoretical results are presented.     

Estimating household structure in ancient China by using historical data: a latent class analysis of partially missing patterns

Summary.  Social data often contain missing information. The problem is inevitably severe when analysing historical data. Conventionally, researchers analyse complete records only. Listwise deletion not only reduces the effective sample size but also may result in biased estimation, depending on the missingness mechanism. We analyse household types by using population registers from ancient China (618–907 AD) by comparing a simple classification, a latent class model of the complete data and a latent class model of the complete and partially missing data assuming four types of ignorable and non-ignorable missingness mechanisms. The findings show that either a frequency classification or a latent class analysis using the complete records only yielded biased estimates and incorrect conclusions in the presence of partially missing data of a non-ignorable mechanism. Although simply assuming ignorable or non-ignorable missing data produced consistently similarly higher estimates of the proportion of complex households, a specification of the relationship between the latent variable and the degree of missingness by a row effect uniform association model helped to capture the missingness mechanism better and improved the model fit.     

外商直接投资对我国三大都市圈技术外溢效应的比较研究

本文对外商直接投资在我国三大都市圈的技术外溢效应进行了比较研究,结果表明,外商直接投资在整体上对三大都市圈的技术外溢效应显著,但不同地区之间存在着明显的差别。三大都市圈应在不断加强对外商直接投资技术外溢的消化吸收能力的同时,注重提升本土的自主创新能力。     

湖北省高校科技成果转化的现状调查与分析

通过对高校科技工作管理者、高校教师以及部分企业的调研发现,目前影响湖北省高校科技成果转化的因素主要是政府管理、资金投入、高校观念转变与机制创新、企业重视等方面,并提出相应的对策与建议.     

浅谈企业知识管理

在知识经济时代 ,知识管理成为企业管理的重要课题。只有当企业充分认识到知识管理的重要性 ,自觉实施有效的知识管理 ,才能使企业在全球激烈的竞争环境中立于不败之地。因此 ,研究企业如何进行知识管理具有重要的理论价值和应用价值。本文从知识管理的涵义和特征入手 ,从几个方面研究企业知识管理的实施办法。     

论阜新经济发展的外向性

文章从市场化的程度、贸易和经济的发展、开放梯度战略以及区域经济布局这四个方面剖析了阜新与经济发达地区的巨大差距及产生差距的原因,阐述了阜新的经济转型、产业结构调整及市场化发育与外向经济的依存关系,特别是从引进项目的基础工作、制定相关优惠政策及提高法律意识等方面,指明了阜新进一步对外开放需要解决和注意的问题。     

江泽民在实践哲学思想上的创新

江泽民同志的实践哲学思想,在继承邓小平实践哲学思想基础上,更具有新的时代特色。实事求是、与时俱进的创新思维是实践哲学思想的灵魂,贯穿于整个实践哲学体系;“三个代表”的思想是对实践标准的新发展,指明了社会主义实践和党的实践的基本目标;实践主体理论的创新,是实现社会主义实践基本目标的有力保障。     

中小企业增长与发展的创新驱动

中小企业的增长与发展是两个既有联系又有区别的概念。增长需要创新,转化为发展时更需要创新作为张力。本文分析了中小企业创新系统并探讨了创新内容以及创新活动中应该注意的问题。     

网络环境下图书馆信息服务创新初探

信息资源网络化给图书馆的生存和发展带来了巨大的冲击,图书馆惟有创新才有出路。本文提出转变观念是信息服务创新的前提;加强网络信息资源的开发利用是信息服务创新的基础;技术创新是信息服务创新的手段;高素质的图书馆员是信息服务创新的关键。