Estimation Bias in Complete-Case Analysis in Crossover Studies with Missing Data

Crossover designs are used often in clinical trials. It is not uncommon that subjects discontinue before completing all treatment periods in a crossover study. Despite availability of statistical methodologies utilizing all available data and software for obtaining valid inferences under the assumption of missing at random (MAR), naïve approaches, such as the complete case (CC) analysis, which is only valid with a strong assumption of missing completely at random are still widely used in practice. In this article, we obtain the analytical form of the estimation bias of treatment effects with CC for linear mixed models. We use simulation studies to examine the inflation of Type I error and efficiency loss in the inferences with CC under MAR. Invalidity and inefficiency of two other commonly used approaches for defining analyzed data in the presence of missing data, including data from at least two periods in three period crossover and available cases for a specific comparison of interest, are also demonstrated through simulation studies.     

A modal method for generating binomial variables

The paper considers the problem of generating binomial random variables when the parameters n and p may vary from call to call (as in the generation of multinomial random variables), A new algorithm, based on sequentially searching alternately down and up from the modal probability, is introduced. This is easy to program and requires no special library facilities It is suitable for microcomputers as well as mainframes Some sample timings are given for a FORTRAN 7 7 implementation     

代次视角下农民工组织参与对政治参与意愿的影响研究——基于西安市1215名农民工的调查

利用2012年“西安市农村流动人口发展状况调查”数据,使用卡方检验和二分Logistic回归,在代次视角下分析农民工政治参与意愿的特征和组织参与对农民工政治参与意愿的影响.研究发现:农民工政治参与意愿具有稳定的制度性偏好,但新生代农民工非制度化参与的风险增加;组织化能够显著提升农民工的政治参与意愿,随着代次更替,作用方向不变,但程度减弱;农民工经济收入的增加,具有同时促进制度化和抑制非制度化参与倾向的作用.     

Performance of standard imputation methods for missing quality of life data as covariate in survival analysis based on simulations from the International Breast Cancer Study Group Trials VI and VII*

Abstract

Imputation methods for missing data on a time-dependent variable within time-dependent Cox models are investigated in a simulation study. Quality of life (QoL) assessments were removed from the complete simulated datasets, which have a positive relationship between QoL and disease-free survival (DFS) and delayed chemotherapy and DFS, by missing at random and missing not at random (MNAR) mechanisms. Standard imputation methods were applied before analysis. Method performance was influenced by missing data mechanism, with one exception for simple imputation. The greatest bias occurred under MNAR and large effect sizes. It is important to carefully investigate the missing data mechanism.     

On the Alias Method for Generating Random Variables from a Discrete Distribution

The alias method of Walker is a clever, new, fast method for generating random variables from an arbitrary, specified discrete distribution. A simple probabilistic proof is given, in terms of mixtures, that the method works for any discrete distribution with a finite number of outcomes. A more efficient version of the table-generating portion of the method is described. Finally, a brief discussion on efficiency of the method is given. We believe that the generality, speed, and simplicity of the method make it attractive for use in generating discrete random variables.     

新一代信息技术产业融资模式的创新绩效研究

目前,我国新一代信息技术产业的各种外源融资模式中仍存在一些问题: 财政补贴重“面”略“点”、信贷融资结构欠佳、股权融资过于集中、商业信用融资“断链”“短链”。实证研究结果显示,企业规模对于企业创新有显著的促进作用,而股权融资变量却与被解释变量呈显著负相关关系,其他解释变量与被解释变量不相关。基于此,新一代信息技术产业融资模式的优化要以创新改革财税支持模式,提高资金使用绩效;以区块链技术嵌入信息平台,创新信贷融资模式;以股权激励促进研发创新,增强产业核心竞争力;以技术链创新发展反哺产业链,加固产业链韧性。     

流动人口二代研究:概念、挑战与进路

人口流动对中国社会的复杂性、持续性影响,要求我们不仅要关注流动人口本身,还要关注流 动人口的子代群体,即本文所说的“流动人口二代”。 尽管既有研究提出了一些与“流动人口二代”近似 的概念,并在代际传递视角下围绕代际关系、身心健康、教育状况、职业发展、社会融入等方面开展了经验 研究,但这些研究都没有直接针对这一群体全貌展开系统考察,没有给出流动人口二代的群体画像、总体 特质,也没有对影响流动人口二代发展的社会事件与生命历程展开讨论。 鉴于此,本研究提出要着眼于 流动人口二代生命历程,聚焦流动人口二代生命历程中的健康风险、聚焦数字化场域下的流动人口二代 职业新发展、聚焦人口结构性变迁背景下的流动人口二代家庭化问题、聚焦新时代新形势下的流动人口 二代社会融入问题、聚焦新型城镇化情境下的流动人口二代政策保障,思考流动人口二代研究的总体性 框架与发展进路。     

农村生活垃圾分类长效机制建设的社会基础

农村生活垃圾分类长效机制建设是农村人居环境整治的重要组成部分。当前生活垃圾分类越来越成为全国各地农村尝试开展与实施的环境治理工程,但如何建立生活垃圾分类长效机制一直困扰着地方环境管理者。通过对浙北码头村的案例分析,总结该村在长期实践中的生活垃圾分类长效机制建设经验以及不同主体参与垃圾分类的行动策略,并深入挖掘长效机制建设背后的社会结构、社会关系、地方文化等社会基础。最后,基于理论分析与实地调查的互动联系,提出内生于村庄社会的制度规范、有效的组织动员结构、可适用的治理技术手段是当前农村生活垃圾分类长效机制建设的社会基础,以此来反映符合农村社会特点、多元主体共同参与的环境治理长效机制建设的理论内涵与实践路径。     

论集中力量办大事的理论意涵与实践趋势——基于“五何”维度的分析

作为充分彰显中国特色社会主义制度显著优势的治国理政模式,集中力量办大事在近年的官方话语和学术研究中均是一个高频使用的重要概念。从内在涵义来看,集中力量办大事具体是指基于科学的决策,立足于全国的整体和大局,在中国共产党的集中统一领导下,调动各方面积极性,科学有效调配各领域各层级资源,集中来解决我国革命、建设和改革中的重大任务、关键问题与突出难题的治国理政模式。从演进过程来看,我们实施的集中力量办大事,既不是自古就有的,也不是中国古代“集中力量办大工程”的沿袭,而是中华人民共和国成立以来历经几代领导集体提炼总结而成的。在我国革命、建设和改革的不同时期,之所以要实行“集中力量办大事”,是由于世情、国情、党情等多重因素共同作用使然。集中力量办大事之所以能有效运行并取得成功,有着深刻而具体的政治、经济、文化和社会等方面的凭借依托机制。从未来实践趋势来看,集中力量办大事这一治国理政模式不仅要长期坚持实践,更要适应新形势和开拓新机制来推进其提升治理效能。