A Simulation Study Comparing Multiple Imputation Methods for Incomplete Longitudinal Ordinal Data

Multiple imputation (MI) is now a reference solution for handling missing data. The default method for MI is the Multivariate Normal Imputation (MNI) algorithm that is based on the multivariate normal distribution. In the presence of longitudinal ordinal missing data, where the Gaussian assumption is no longer valid, application of the MNI method is questionable. This simulation study compares the performance of the MNI and ordinal imputation regression model for incomplete longitudinal ordinal data for situations covering various numbers of categories of the ordinal outcome, time occasions, sample sizes, rates of missingness, well-balanced, and skewed data.     

Choice of estimand and analysis methods in diabetes trials with rescue medication

The analysis of clinical trials aiming to show symptomatic benefits is often complicated by the ethical requirement for rescue medication when the disease state of patients worsens. In type 2 diabetes trials, patients receive glucose‐lowering rescue medications continuously for the remaining trial duration, if one of several markers of glycemic control exceeds pre‐specified thresholds. This may mask differences in glycemic values between treatment groups, because it will occur more frequently in less effective treatment groups. Traditionally, the last pre‐rescue medication value was carried forward and analyzed as the end‐of‐trial value. The deficits of such simplistic single imputation approaches are increasingly recognized by regulatory authorities and trialists. We discuss alternative approaches and evaluate them through a simulation study. When the estimand of interest is the effect attributable to the treatments initially assigned at randomization, then our recommendation for estimation and hypothesis testing is to treat data after meeting rescue criteria as deterministically ‘missing’ at random, because initiation of rescue medication is determined by observed in‐trial values. An appropriate imputation of values after meeting rescue criteria is then possible either directly through multiple imputation or implicitly with a repeated measures model. Crucially, one needs to jointly impute or model all markers of glycemic control that can lead to the initiation of rescue medication. An alternative for hypothesis testing only are rank tests with outcomes from patients ‘requiring rescue medication’ ranked worst, and non‐rescued patients ranked according to final visit values. However, an appropriate ranking of not observed values may be controversial. Copyright © 2015 John Wiley & Sons, Ltd.     

《侵权责任法》医疗损害责任归责原则体系评析

《侵权责任法》第七章"医疗损害责任"立足司法实践,借鉴域外经验,创设了一般归责原则与特殊归责原则相结合的归责原则体系,有利于依法平衡医患利益与妥善解决医患纷争。这一体系的设计也存在一些问题,造成各种归责原则之间逻辑不清,界限不明,影响《侵权责任法》的准确理解与正确适用。建议有关部门尽快制定相关司法解释,为准确适用法律提供参考。     

美国产品责任法上的售后义务及其对中国的启示

生产商售后义务是产品责任法中的一项新制度,它起源于美国。该制度在美国已经发展得相对成熟,它对所包含的售后警告和售后召回产品义务的具体判断都形成了一套较成熟的标准。对生产商售后义务与工艺水平抗辩、产品改进的特殊关系,以及违反售后义务致害责任的归责原则上,美国司法判决都已经比较完善。这些经验对我国当下《侵权责任法》第46条售后义务条款的实施具有理论和现实的指导意义。     

协商互动在大学英语课堂中运用的可行性研究

"协商"在SLA研究中指学习者与其对话者为克服交际障碍而做出的各种会话调整或修饰,它直接影响目的语输入和输出的质量。本文在回顾协商互动的理论依据和国内外研究现状的基础上,从协商互动对学习者二语习得的作用的角度,分析其在大学英语课堂中运用的可行性及其在大学英语课堂教学中的运作模式。     

完善“两课”教学评价机制，提高大学生的创新素质

“两课”教学评价机制的完善是提高大学生创新素质的重要保证。我们要以促进学生的发展为目的 ,鼓励学生的创新为导向 ,来确定“三个课堂有机结合”的“知、情、意、信、行”相互渗透融合的综合评价内容体系 ,来选择教师评价与学生自我评价相结合的多评价主体参与的评价方法     

适应素质教育要求 更新"两课"教育理念

"两课"是高校实旌素质教育的内在环节和重要内容。在素质教育中真正发挥"两课"的思想政治主渠道作用,必须更新教育理念,正确认识和处理好"两课"教育的社会功能和本体功能的关系、"两课"教育的知识体系与价值体系的关系、"两课"教育的"晓之以理"和"动之以情"的关系。     

Imputation by power transformation

In this paper, a new power transformation estimator of population mean in the presence of non-response has been suggested. The estimator of mean obtained from proposed technique remains better than the estimators obtained from ratio or mean methods of imputation. The mean squared error of the resultant estimator is less than that of the estimator obtained on the basis of ratio method of imputation for the optinum choice of parameters. An estimator for estimating a parameter involved in the process of new method of imputation has been discussed. The MSE expressions for the proposed estimators have been derived analytically and compared empirically. Product method of imputation for negatively correlated variables has also been introduced. The work has been extended to the case of multi-auxiliary information to be used for imputation.     

Distribution estimation with auxiliary information for missing data

There is much literature on statistical inference for distribution under missing data, but surprisingly very little previous attention has been paid to missing data in the context of estimating distribution with auxiliary information. In this article, the auxiliary information with missing data is proposed. We use Zhou, Wan and Wang's method (2008) to mitigate the effects of missing data through a reformulation of the estimating equations, imputed through a semi-parametric procedure. Whence we can estimate distribution and the τth quantile of the distribution by taking auxiliary information into account. Asymptotic properties of the distribution estimator and corresponding sample quantile are derived and analyzed. The distribution estimators based on our method are found to significantly outperform the corresponding estimators without auxiliary information. Some simulation studies are conducted to illustrate the finite sample performance of the proposed estimators.     

Partitioned difference families and almost difference sets

Partitioned difference families (PDFs) were first studied by Ding and Yin in conjunction with the construction of constant composition codes (CCCs). In 2008, Yin et al. presented the constructions of a number of infinite classes of PDFs based on known difference sets in GF(q). In this paper, we further investigate the constructions of PDFs by using known almost difference sets in GF(q), and establish some recursive constructions of PDFs. As their applications, we also get a number of perfect difference systems of sets (DSSs) over Z_q² with q odd prime.