Type I error rates from likelihood‐based repeated measures analyses of incomplete longitudinal data

The last observation carried forward (LOCF) approach is commonly utilized to handle missing values in the primary analysis of clinical trials. However, recent evidence suggests that likelihood‐based analyses developed under the missing at random (MAR) framework are sensible alternatives. The objective of this study was to assess the Type I error rates from a likelihood‐based MAR approach – mixed‐model repeated measures (MMRM) – compared with LOCF when estimating treatment contrasts for mean change from baseline to endpoint (Δ). Data emulating neuropsychiatric clinical trials were simulated in a 4 × 4 factorial arrangement of scenarios, using four patterns of mean changes over time and four strategies for deleting data to generate subject dropout via an MAR mechanism. In data with no dropout, estimates of Δ and SE_Δ from MMRM and LOCF were identical. In data with dropout, the Type I error rates (averaged across all scenarios) for MMRM and LOCF were 5.49% and 16.76%, respectively. In 11 of the 16 scenarios, the Type I error rate from MMRM was at least 1.00% closer to the expected rate of 5.00% than the corresponding rate from LOCF. In no scenario did LOCF yield a Type I error rate that was at least 1.00% closer to the expected rate than the corresponding rate from MMRM. The average estimate of SE_Δ from MMRM was greater in data with dropout than in complete data, whereas the average estimate of SE_Δ from LOCF was smaller in data with dropout than in complete data, suggesting that standard errors from MMRM better reflected the uncertainty in the data. The results from this investigation support those from previous studies, which found that MMRM provided reasonable control of Type I error even in the presence of MNAR missingness. No universally best approach to analysis of longitudinal data exists. However, likelihood‐based MAR approaches have been shown to perform well in a variety of situations and are a sensible alternative to the LOCF approach. MNAR methods can be used within a sensitivity analysis framework to test the potential presence and impact of MNAR data, thereby assessing robustness of results from an MAR method. Copyright © 2004 John Wiley & Sons, Ltd.     

“最后一公里”问题的原因与解决对策

农业信息化建设中的"最后一公里"问题,严重影响了农业信息化的经济效果。依据经济学中消费者最优决策的等边际理论,分析了农民不进行网络投资的合理性;在对比了计算机网络给农民带来的效用与为此支付成本的基础上,区别了信息的获取成本和消费成本两个不同的概念;在考察了农业信息系统现状的同时,提出了增加信息产品有效供给,采用商业化的运作模式,进行农业生产与经营相分离的农业组织化改革等对策。     

清朝末年有关农业政策的实施

清末重农与传统的重本抑末不同,它是从推动工商业发展的角度支持农业发展,采取了兴办农业教育、组建农会组织、鼓励农业垦殖等一系列兴农政策措施,推动了中国传统农业近代化。但由于封建制度性障碍,清末朝庭的腐败,中国近代农业发展仍相当缓慢。     

论19世纪末年的社会心态

自戊戌变法后期清朝政府守旧派掌控朝政始的19世纪末年,趋新的社会风气转为沉闷;特别是义和团运动时期,守旧派将其仇新、排外的情绪推向极至,直接导引了普通民众的冷漠与无知、新式知识分子的压抑与彷徨心态。     

中韩端午节祭之关联性论略

中韩两国的民间风俗节日中，都有“端午节”。从内容与形式来看，二者存在着较多的差异性，即是各具民族性与地域性。但是，二者的关联性也是非常清楚的。从风行的时代范围来说，中国式的端午节较早，而韩国式的端午节较迟。从活动内容来说，韩国式的端午节仍有许多方面是延续了中国式端午节的实质内容的。     

Teaching Causation in History

Social studies teachers have an obligation to help students grapple with and thoughtfully examine controversial issues, often in a contemporary context. One such issue is the U.S. use of unmanned aerial vehicles, generally known as drones. Whether for surveillance purposes or military missions, the use of drones by the U.S. government has preceded the development of clearly articulated policy guidelines. This article examines the use of drones in U.S. policy, the argument for and against their deployment, and the manner in which social studies educators may effectively teach their students about such a complex, challenging topic. Toward that end, the article also advocates for the use of an ethical and analytical framework, the “just war” doctrine, which can assist students in critiquing how drones are used, under what conditions, and the social impact that may entail.     

精益建筑重要工具——最后计划者技术研究

文章首先介绍了“精益建筑”的概念，然后由建筑生产基本理论缺失、工具方法不能适应日益复杂的项目环境，引出精益建筑的重要工具——最后计划者LP（Last Planner）技术，并将传统计划系统与LP系统进行了比较，说明了LP系统的优势。最后对LP方法在国内的使用提出了建议。     

试论满族家祭与萨满教的关系

满族家祭与萨满教的关系是萨满教研究的一个重要问题,本文通过历史源流的分析,确定家祭来源于萨满教,同时又分析了家祭与萨满教的区别,最后认为满族家祭是萨满教的末期形态。     

辛亥前刘师培的《左传》研究

《左传》乃中国古代十分重要的儒家典籍,辛亥前刘师培的《左传》研究驳斥今文经学家关于《左传》为刘歆伪造的观点,认为《左传》的基本精神与《春秋》大义相符,同时对《左传》在后世不显的情况进行了分析,体现了强烈的时代气息。     

1946-1952年土改小说创作潮流初探

土地改革小说创作潮流在20世纪四五十年代伴随着土地改革运动而起,是一种特定时代特定题材的文学书写思潮。通过史料发掘和作品重读会发现,这股声势浩大的创作潮流长期以来被研究者简化,导致土改小说创作研究长期处于滞后状态。从宏观角度来看,这股创作潮流的发生与推进,既源自延安文艺理论与运动的指引,也是广大作家对中国共产党领导下的农村土地变革之配合与跟进,从这些作品中折射出了延安文人精神层面的变化与矛盾。