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.     

发展是反贫困的核心问题--广西百色反贫困研究之三

发展是反贫困的主题。发展是解决贫困问题的关键。必须用加快发展的办法解决贫困问题。     

农业产业化是我国农业发展的必由之路

农业产业化作为市场经济条件下发展农业的一种主张,引起我国理论界和经济界的广泛关注和讨论.本文从我国的农业现状出发,对我国实施农业产业化的必然性和可行性进行了论证,从而证明农业产业化是我国农业发展的必然选择.同时简要回顾我国农业产业化的发展历程,指出其存在问题,并提出对策,以期农业产业化在我国健康发展.     

在生物进化与人类进化之间

由于人类的进化已日益集中反映在文化的进化上 ,从而使得它与生物之间表现出不同的性质和方式。对于属人世界的生物进化来说 ,既存在自然选择式的客体中介 ,又存在社会选择式的主体中介 ,在当今世界所普遍存在的“生态危机”和各种“人类危机”面前 ,我们更需要确立和谐型的社会选择     

近代中国整合中西文化冲突的价值选择模式及现代启示

中国近代文化变迁的过程 ,在一定意义上表现为中西文化的冲突与整合的过程。为整合中西文化冲突 ,近代中国先后采取了文化传统主义、文化折中主义、文化虚无主义与文化综合创新等价值选择模式。近代文化整合的经验教训启示我们 ,在新时期文化建设问题上 ,必须正确处理文化的一元与多元、整体性与可分性、时代性与民族性的关系 ,坚持走综合创新之路     

Merging information for semiparametric density estimation

Summary.  The density ratio model specifies that the likelihood ratio of m −1 probability density functions with respect to the m th is of known parametric form without reference to any parametric model. We study the semiparametric inference problem that is related to the density ratio model by appealing to the methodology of empirical likelihood. The combined data from all the samples leads to more efficient kernel density estimators for the unknown distributions. We adopt variants of well-established techniques to choose the smoothing parameter for the density estimators proposed.     

编辑主体性简论

编辑活动在中国已有上千年的历史,几乎与文化相伴而生,但又比文化更多几分主观观照。编辑是文明的阶梯,引导人们从蒙昧走向文明,其鲜明的方向性就在于编辑具有主体性。从中国文化发展的历程说明编辑主体性的重要性,阐述了编辑主体性的内涵,最后从中国现代化建设的现实需要出发,指出广大编辑工作者应充分发挥主体性,肩负起对时代的伟大责任。