A modified random-effect procedure for combining risk difference in sets of 2×2 tables from clinical trials

Summary Meta-analyses of sets of clinical trials often combine risk differences from several 2×2 tables according to a random-effects model. The DerSimonian-Laird random-effects procedure, widely used for estimating the populaton mean risk difference, weights the risk difference from each primary study inversely proportional to an estimate of its variance (the sum of the between-study variance and the conditional within-study variance). Because those weights are not independent of the risk differences, however, the procedure sometimes exhibits bias and unnatural behavior. The present paper proposes a modified weighting scheme that uses the unconditional within-study variance to avoid this source of bias. The modified procedure has variance closer to that available from weighting by ideal weights when such weights are known. We studied the modified procedure in extensive simulation experiments using situations whose parameters resemble those of actual studies in medical research. For comparison we also included two unbiased procedures, the unweighted mean and a sample-size-weighted mean; their relative variability depends on the extent of heterogeneity among the primary studies. An example illustrates the application of the procedures to actual data and the differences among the results. This research was supported by Grant HS 05936 from the Agency for Health Care Policy and Research to Harvard University.     

对欠发达地区农村信用社运行效率的分析

农村信用社改革及其运行效率是当前中国金融界的一个重要课题,农村信用社运行效率的高低依赖于改革的主导力量及其模式的具体选择。中国农村信用社已经历了多次在政府主导下进行的反反复复的体制性变迁,产权制度及治理结构问题未能得到有效解决,其运行效率较低。结合在江西若干县(区)的调查,对欠发达地区农村信用社运行效率进行了分析,并提出了提升农村信用社运行效率的对策建议。     

税收征管效率综合评价指标体系研究

税收征管效率是评价税务机关工作效果的主要指标,而评价指标体系的确定是科学评价税收征管效率的基础和重点。本文分析了税收征管效率的内涵及外延,通过实证建立了税收征管效率的综合评价指标体系。     

Marginal and association regression models for longitudinal binary data with drop‐outs: A likelihood‐based approach

Longitudinal data often contain missing observations, and it is in general difficult to justify particular missing data mechanisms, whether random or not, that may be hard to distinguish. The authors describe a likelihood‐based approach to estimating both the mean response and association parameters for longitudinal binary data with drop‐outs. They specify marginal and dependence structures as regression models which link the responses to the covariates. They illustrate their approach using a data set from the Waterloo Smoking Prevention Project They also report the results of simulation studies carried out to assess the performance of their technique under various circumstances.     

我国市场经济的价值取向--思想政治教育内容探讨之二

文章根据我国市场经济的性质以及市场经济在发展过程中对社会生活各方面所产生的不同影响,分析论证了我国市场经济的价值取向是经济价值、政治价值和思想文化价值三者的统一.     

论实现效率的市场机制与实现公平的民主机制

强调公平和效率优先历来是两种不同的价值取向。一个成熟的执政党和一个健康的社会应提供两种阶值取向同时存在、进行辩论的自由空间,建立体现两种价值取向的市场经济机制和民主政治机制,培育兼容这两种价值取向、维护这两大机制的文化土壤,为构建社会主义和谐社会奠定坚实的经济、政治和文化基础。     

冗员失业、社会负担与国有企业效率

影响国有企业效率的因素有很多,其中制度因素最为重要。而在传统的国有企业制度下,冗员失业和社会负担又是制约企业效率提高的关键。时至今日,这个问题仍是国有企业进行减员增效改革、实施战略性重组的最大障碍。从理论上研究冗员失业对企业效率的影响,并结合我国实际情况分析社会负担给国有企业造成的压力,以强化社会保障为突破口,提出解决冗员失业和社会负担问题、提高国有企业效率的具体对策。     

公共物品的提供模式及政府管制的效率比较

随着技术水平以及人们收入水平的不断提高,市场力量不断进入到公共物品的提供领域,然而由于公共物品对于社会公平、公正带来的重要影响,政府会对市场提供公共物品时进行有效管制,而最主要的管制模式就是进行价格管理。文章利用Wickstro¨m(2001)的模型,分析了政府在对市场提供公共物品进行管制时的效率问题,指出在成本信息不对称时政府管制的效率可能很低,反而给社会福利造成了比较大的损失,同时企业利润也受到影响。     

随机型细胞神经网络的稳定性

借助于李雅谱洛夫理论、矩阵分析方法和It?公式,结合不等式分析技巧,研究了随机细胞神经网络系统的均方指数稳定性,给出了系统的解的二阶矩Liapunov指数估计式和均方指数稳定的充分条件。     

Improving flexibility and efficiency by adding parallelism to genetic algorithms

In this paper we develop a study on several types of parallel genetic algorithms (PGAs). Our motivation is to bring some uniformity to the proposal, comparison, and knowledge exchange among the traditionally opposite kinds of serial and parallel GAs. We comparatively analyze the properties of steady-state, generational, and cellular genetic algorithms. Afterwards, this study is extended to consider a distributed model consisting in a ring of GA islands. The analyzed features are the time complexity, selection pressure, schema processing rates, efficacy in finding an optimum, efficiency, speedup, and resistance to scalability. Besides that, we briefly discuss how the migration policy affects the search. Also, some of the search properties of cellular GAs are investigated. The selected benchmark is a representative subset of problems containing real world difficulties. We often conclude that parallel GAs are numerically better and faster than equivalent sequential GAs. Our aim is to shed some light on the advantages and drawbacks of various sequential and parallel GAs to help researchers using them in the very diverse application fields of the evolutionary computation.