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Craig H. Mallinckrodt Christopher J. Kaiser John G. Watkin Michael J. Detke Geert Molenberghs Raymond J. Carroll 《Pharmaceutical statistics》2004,3(3):171-186
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 SEΔ 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 SEΔ from MMRM was greater in data with dropout than in complete data, whereas the average estimate of SEΔ 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. 相似文献
23.
王楠 《西安石油大学学报(社会科学版)》2003,12(1):54-57,92
衍生金融工具因具有高风险性、时态未来性及品种多样性等特点,其计量问题一直是会计核算的核心和难点。传统的会计计量理论和方法已无法满足其要求。为此,有必要改进现行的会计核算体制,以公允价值取代历史成本对衍生金融工具进行计量,以增强信息披露的力度。 相似文献
24.
For a wide variety of applications, experiments are based on units ordered over time or space. Models for these experiments generally may include one or more of: correlations, systematic trends, carryover effects and interference effects. Since the standard optimal block designs may not be efficient in these situations, orthogonal arrays of type I and type II, which were introduced in 1961 by C.R. Rao [Combinatorial arrangements analogous to orthogonal arrays, Sankhya A 23 (1961) 283–286], have been recently used to construct optimal and efficient designs for many of these experiments. Results in this area are unified and the salient features are outlined. 相似文献
25.
任春雷 《沈阳师范大学学报(社会科学版)》2008,32(5):9-12
风险社会的来临改变了人类的生存境遇和生活体验,也必将导致人们观念和行为方式的改变。对现代风险社会进行认真的反思,并将与“人为的不确定性”相联系的风险概念引入,可以消解历史决定论的思维定势,也可以为马克思历史唯物主义的真实意蕴及当代性的彰显提供全新的解释维度和现实根据。 相似文献
26.
评鲍德里亚的"消费社会理论" 总被引:14,自引:0,他引:14
余源培 《复旦学报(社会科学版)》2008,42(1):15-22
鲍德里亚系统提出了"消费社会"的理论。他企图对唯物史观进行"颠覆"是错误的。但是不能简单地认为他是资本主义制度的辩护士。鲍德里亚不懂得马克思从根本上颠覆了国民经济学和唯心主义历史观的两种"幻象",从而奠定了生产和劳动对于人类社会存在与发展的基础性地位;不懂得消费与生产的现实辩证关系,片面地离开生产探讨消费的新特征,甚至主张用消费取代生产。消费异化是劳动异化的表现。技术救赎不可能解决当代人类面临的重大社会问题。 相似文献
27.
张启祥 《扬州大学学报(人文社会科学版)》2008,12(6):40-44
历史上的儒商以市场为枢纽,以资源整合为契机,以儒商特有的商业精神和价值体系,在国家、民生、市场和企业间寻找到一定的内在关系和共同点,并形成规模和品牌,为新兴都市的发展作出了贡献。其“得利及人”的核心价值体系,既是近代儒商自身发展的需要,也是社会和地区发展的需要,是融企业使命与社会责任于一体的区域发展本质的具体体现,更是长三角城市带崛起所以能取得现在这样成就的根本所在。在贯彻科学发展观的今天,儒商思想是实现可持续发展的重要精神武器。 相似文献
28.
马桂萍 《南华大学学报(社会科学版)》2003,4(4):45-47
毛泽东农村调查研究方法是一个完整的科学体系,马克思的辩证唯物主义和历史唯物主义是毛泽东农村调查研究方法的理论基础,即方法论。矛盾分析法和阶级分析法是毛泽东农村调查研究的基本方法。典型调查、类型调查、普遍调查、实地访问、开调查会、表格调查法、文献法、历史法等是毛泽东农村调查研究的方式和具体方法。 相似文献
29.
张秀华 《云南民族大学学报(哲学社会科学版)》2003,20(4):55-59
本文简要介绍了云南最重要的几种方志,对云南方志的五个特征:地方性、广泛性、资料性、真实性与民族性进行了论述,分析了云南志的价值,并讨论了开发利用情况。 相似文献
30.
Craig H. Mallinckrodt John G. Watkin Geert Molenberghs Raymond J. Carroll 《Pharmaceutical statistics》2004,3(3):161-169
Missing data, and the bias they can cause, are an almost ever‐present concern in clinical trials. The last observation carried forward (LOCF) approach has been frequently utilized to handle missing data in clinical trials, and is often specified in conjunction with analysis of variance (LOCF ANOVA) for the primary analysis. Considerable advances in statistical methodology, and in our ability to implement these methods, have been made in recent years. Likelihood‐based, mixed‐effects model approaches implemented under the missing at random (MAR) framework are now easy to implement, and are commonly used to analyse clinical trial data. Furthermore, such approaches are more robust to the biases from missing data, and provide better control of Type I and Type II errors than LOCF ANOVA. Empirical research and analytic proof have demonstrated that the behaviour of LOCF is uncertain, and in many situations it has not been conservative. Using LOCF as a composite measure of safety, tolerability and efficacy can lead to erroneous conclusions regarding the effectiveness of a drug. This approach also violates the fundamental basis of statistics as it involves testing an outcome that is not a physical parameter of the population, but rather a quantity that can be influenced by investigator behaviour, trial design, etc. Practice should shift away from using LOCF ANOVA as the primary analysis and focus on likelihood‐based, mixed‐effects model approaches developed under the MAR framework, with missing not at random methods used to assess robustness of the primary analysis. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献