Properties of the weighted log‐rank test in the design of confirmatory studies with delayed effects

Proportional hazards are a common assumption when designing confirmatory clinical trials in oncology. This assumption not only affects the analysis part but also the sample size calculation. The presence of delayed effects causes a change in the hazard ratio while the trial is ongoing since at the beginning we do not observe any difference between treatment arms, and after some unknown time point, the differences between treatment arms will start to appear. Hence, the proportional hazards assumption no longer holds, and both sample size calculation and analysis methods to be used should be reconsidered. The weighted log‐rank test allows a weighting for early, middle, and late differences through the Fleming and Harrington class of weights and is proven to be more efficient when the proportional hazards assumption does not hold. The Fleming and Harrington class of weights, along with the estimated delay, can be incorporated into the sample size calculation in order to maintain the desired power once the treatment arm differences start to appear. In this article, we explore the impact of delayed effects in group sequential and adaptive group sequential designs and make an empirical evaluation in terms of power and type‐I error rate of the of the weighted log‐rank test in a simulated scenario with fixed values of the Fleming and Harrington class of weights. We also give some practical recommendations regarding which methodology should be used in the presence of delayed effects depending on certain characteristics of the trial.     

电子档案管理探微

电子档案是信息技术不断发展的产物,将逐步成为档案管理的主要对象。在分析我国电子档案管理现状的基础上,文章着重探讨了保证电子档案的凭证性的技术措施和管理措施,同时讨论了如何科学、有效地提供电子档案利用。     

做好新时期高校的人事档案工作

合并后高校的人事档案管理部门由于原先各校的管理水平存在着差异,档案内容缺乏完整性,失实现象有所存在,这些都给档案管理人员带来了繁重的工作量。充分调动档案工作人员的积极性,管理人员建立优良的服务意识,畅通人事档案材料来源渠道,档案工作实现网络化,是做好新时期人事档案工作的关键。     

基于Web日志和商品分类的协同过滤推荐系统

传统的协同过滤算法一般以用户对商品的评分作为研究,考虑到显式的评分数据一般很少能够取到,本文从记录用户浏览历史的服务器端日志文件以及客户购买历史数据作为数据源,根据商品分类进行评分矩阵设计,最后由此得到最近邻居从而给予个性化推荐,试验证明推荐效果比较显著。     

家庭档案及其教育功能探析

家庭档案在人们社会生活中的重要作用日益凸显;就教育功能而言,突出地表现在家庭档案可以提供德智体、美育、心育等方面的教育内容;同时,家庭档案也是一种积极有效的教育手段:能促进自主学习与自我教育,有利于家庭积极参与社区教育和社会主义精神文明建设;能促进学校的教育教学工作,有利于家教合作。档案部门、家庭、学校等有关方面应积极协作,加强宣传力度,加强公众的档案意识,向公众提供建设家庭档案的业务指导,加强家庭档案的建设,以充分发挥其教育功能。     

The Box–Cox Transformation and Non‐Iterative Estimation Methods for Ordinal Log‐Linear Models

Recently Beh and Farver investigated and evaluated three non‐iterative procedures for estimating the linear‐by‐linear parameter of an ordinal log‐linear model. The study demonstrated that these non‐iterative techniques provide estimates that are, for most types of contingency tables, statistically indistinguishable from estimates from Newton's unidimensional algorithm. Here we show how two of these techniques are related using the Box–Cox transformation. We also show that by using this transformation, accurate non‐iterative estimates are achievable even when a contingency table contains sampling zeros.     

Joint Modelling of Survival and Longitudinal Data with Informative Observation Times

In this paper, we consider the joint modelling of survival and longitudinal data with informative observation time points. The survival model and the longitudinal model are linked via random effects, for which no distribution assumption is required under our estimation approach. The estimator is shown to be consistent and asymptotically normal. The proposed estimator and its estimated covariance matrix can be easily calculated. Simulation studies and an application to a primary biliary cirrhosis study are also provided.     

Large sample bias of maximum likeihood estimates from a series of sparse ixj tables

For a large series of IxJ tables, each containing two observations, the bias of the maximum likelihood estimates of log linear partial association parameters is shown to be equal to the parameters, regardless of the size of I and J. The partial association considered is that between row and column variables; the three way interactions are assumed to be O. This is a generalization of Andersen's results (1973a, 1973b) for a series of 2x2 tables.     

A property of coefficients of variation for ordered bivariate log-normal variables

This paper considers the maximum and minimum of a pair of log-normal variables with equal mean. It shows that either order statistic has a smaller coefficient of variation than the two original log-normal variables provided the latter are of equal variance. When the variances are unequal, as the variance ratio increases, the minimum (maximum), has a smaller coefficient of variation if the correlation coefficient of the log-normal variables is small (small) and the variances are large (small).