Estimating the variance for heterogeneity in arm‐based network meta‐analysis

Network meta‐analysis can be implemented by using arm‐based or contrast‐based models. Here we focus on arm‐based models and fit them using generalized linear mixed model procedures. Full maximum likelihood (ML) estimation leads to biased trial‐by‐treatment interaction variance estimates for heterogeneity. Thus, our objective is to investigate alternative approaches to variance estimation that reduce bias compared with full ML. Specifically, we use penalized quasi‐likelihood/pseudo‐likelihood and hierarchical (h) likelihood approaches. In addition, we consider a novel model modification that yields estimators akin to the residual maximum likelihood estimator for linear mixed models. The proposed methods are compared by simulation, and 2 real datasets are used for illustration. Simulations show that penalized quasi‐likelihood/pseudo‐likelihood and h‐likelihood reduce bias and yield satisfactory coverage rates. Sum‐to‐zero restriction and baseline contrasts for random trial‐by‐treatment interaction effects, as well as a residual ML‐like adjustment, also reduce bias compared with an unconstrained model when ML is used, but coverage rates are not quite as good. Penalized quasi‐likelihood/pseudo‐likelihood and h‐likelihood are therefore recommended.     

产品责任跨国诉讼可行性考察

中国消费者受到外国产品伤害的事件屡见不鲜,但维权面临困境.中国受害人近年尝试去美国起诉美国生产商,尽管还未有胜诉案例,但通过调解获得圆满赔偿的案例不少.美国法院一方面通过“长臂管辖”扩大司法管辖权,另一方面通过“不方便法院”原则限制外国原告到美国起诉美国生产商.选择适用何种原则,完全取决于能否保护美国当事人利益.中国消费者应了解美国法律本质并加以利用,达到维权目的.产品责任跨国诉讼有诸多优势,是目前解决中国产品责任纠纷的途径之一.     

改革开放以来的兰州市人口演变的特点

改革开放以来,兰州市人口数量、质量都发生了不小的变化。本文利用统计资料、人口普查资料分析了兰州市人口变化的特点,并提出了一些建议。     

新疆生产建设兵团人口素质刍议

新疆生产建设兵团是新中国成立的第一个寓兵于农、担负着保卫边疆、建设边疆使命的特殊的社会集团组织,也是至今全国惟一保留下来的兵团。本文着重探讨了目前新疆生产建设兵团人口素质下降的原因及提高人口素质的几点建议。     

Accounting for uncertainty in the historical response rate of the standard treatment in single‐arm two‐stage designs based on Bayesian power functions

In phase II single‐arm studies, the response rate of the experimental treatment is typically compared with a fixed target value that should ideally represent the true response rate for the standard of care therapy. Generally, this target value is estimated through previous data, but the inherent variability in the historical response rate is not taken into account. In this paper, we present a Bayesian procedure to construct single‐arm two‐stage designs that allows to incorporate uncertainty in the response rate of the standard treatment. In both stages, the sample size determination criterion is based on the concepts of conditional and predictive Bayesian power functions. Different kinds of prior distributions, which play different roles in the designs, are introduced, and some guidelines for their elicitation are described. Finally, some numerical results about the performance of the designs are provided and a real data example is illustrated. Copyright © 2016 John Wiley & Sons, Ltd.     

塔机主臂杆三维裂纹应力强度因子的计算

采用三维裂纹奇异单元列式方法对含纵向闭合裂纹塔机主臂杆接头部位进行了应力分析和应力强度因子的计算,分析了焊接残余应力对塔机主臂杆母材强度、环向拉应力和应力强度因子的影响。     

戴明循环在教学中的应用

文章介绍了戴明循环,并结合教学实际,阐述了戴明循环"计划-实施-检查-反馈"四个环节在教学实践中应用的要点,提出了运用戴明循环是持续改进教学方法、不断提高教学质量的行之有效的方法.     

Fit for purpose: issues from practice placements,practice teaching and the assessment of students' practice

This paper explores a number of significant issues regarding the delivery of practice based learning for qualifying social workers, in the context of plans for the new social work degree. We also discuss four particular issues: 1. the definition and measurement of ‘good enough’ practice;

2. the determination of students' suitability for social work;

3. the role of practice teachers in responding to sensitive information and students facing personal crises; and

4. specialist and ‘long‐arm’ practice teaching.

In doing so, we draw on both our own direct experience and on discussions between over 70 practice teachers, tutors and placement co‐ordinators attending a Mid‐Yorkshire Social Work Education and Training Planning Group (MYSWETPG) conference hosted by Bradford College in March 2001.

We conclude that, given the current difficulties in the field of qualifying training and education for social workers, any significant improvements following from the new degree will remain dependent on the provision of adequate funding for practice learning, in general, and for the training, structured support and affirmation of practice teachers, in particular.     

Some practical considerations in three‐arm non‐inferiority trial design

Non‐inferiority trials aim to demonstrate whether an experimental therapy is not unacceptably worse than an active reference therapy already in use. When applicable, a three‐arm non‐inferiority trial, including an experiment therapy, an active reference therapy, and a placebo, is often recommended to assess assay sensitivity and internal validity of a trial. In this paper, we share some practical considerations based on our experience from a phase III three‐arm non‐inferiority trial. First, we discuss the determination of the total sample size and its optimal allocation based on the overall power of the non‐inferiority testing procedure and provide ready‐to‐use R code for implementation. Second, we consider the non‐inferiority goal of ‘capturing all possibilities’ and show that it naturally corresponds to a simple two‐step testing procedure. Finally, using this two‐step non‐inferiority testing procedure as an example, we compare extensively commonly used frequentist p ‐value methods with the Bayesian posterior probability approach. Copyright © 2016 John Wiley & Sons, Ltd.     

Do single‐arm trials have a role in drug development plans incorporating randomised trials?

Often, single‐arm trials are used in phase II to gather the first evidence of an oncological drug's efficacy, with drug activity determined through tumour response using the RECIST criterion. Provided the null hypothesis of ‘insufficient drug activity’ is rejected, the next step could be a randomised two‐arm trial. However, single‐arm trials may provide a biased treatment effect because of patient selection, and thus, this development plan may not be an efficient use of resources. Therefore, we compare the performance of development plans consisting of single‐arm trials followed by randomised two‐arm trials with stand‐alone single‐stage or group sequential randomised two‐arm trials. Through this, we are able to investigate the utility of single‐arm trials and determine the most efficient drug development plans, setting our work in the context of a published single‐arm non‐small‐cell lung cancer trial. Reference priors, reflecting the opinions of ‘sceptical’ and ‘enthusiastic’ investigators, are used to quantify and guide the suitability of single‐arm trials in this setting. We observe that the explored development plans incorporating single‐arm trials are often non‐optimal. Moreover, even the most pessimistic reference priors have a considerable probability in favour of alternative plans. Analysis suggests expected sample size savings of up to 25% could have been made, and the issues associated with single‐arm trials avoided, for the non‐small‐cell lung cancer treatment through direct progression to a group sequential randomised two‐arm trial. Careful consideration should thus be given to the use of single‐arm trials in oncological drug development when a randomised trial will follow. Copyright © 2015 The Authors. Pharmaceutical Statistics published by JohnWiley & Sons Ltd.