An Asymptotic Analysis of the Logrank Test

Asymptotic expansions for the null distribution of the logrank statistic and its distribution under local proportional hazards alternatives are developed in the case of iid observations. The results, which are derived from the work of Gu (1992) and Taniguchi (1992), are easy to interpret, and provide some theoretical justification for many behavioral characteristics of the logrank test that have been previously observed in simulation studies. We focus primarily upon (i) the inadequacy of the usual normal approximation under treatment group imbalance; and, (ii) the effects of treatment group imbalance on power and sample size calculations. A simple transformation of the logrank statistic is also derived based on results in Konishi (1991) and is found to substantially improve the standard normal approximation to its distribution under the null hypothesis of no survival difference when there is treatment group imbalance. This revised version was published online in July 2006 with corrections to the Cover Date.     

Optimal Bayesian Randomization

Randomization is a puzzle for Bayesians. The intuitive need for randomization is clear, but there is a standard result that Bayesians need not randomize. In this paper we propose a model in which randomization is a strictly optimal procedure. The most important aspect of our model is that there are several parties who make different decisions and observe different data. The result also sheds light on the ethical considerations involving randomization in a clinical trial.     

谈对青年教师的“传帮带”

针对课程特点,结合多年的教学经验,总结论述了"机械制图"课程教学中,如何对青年教师传帮带的一些做法和体会,意在对理工科专业基础课和专业课青年教师的培养起到借鉴作用。     

Methods for exploring treatment effect heterogeneity in subgroup analysis: an application to global clinical trials

Multi‐country randomised clinical trials (MRCTs) are common in the medical literature, and their interpretation has been the subject of extensive recent discussion. In many MRCTs, an evaluation of treatment effect homogeneity across countries or regions is conducted. Subgroup analysis principles require a significant test of interaction in order to claim heterogeneity of treatment effect across subgroups, such as countries in an MRCT. As clinical trials are typically underpowered for tests of interaction, overly optimistic expectations of treatment effect homogeneity can lead researchers, regulators and other stakeholders to over‐interpret apparent differences between subgroups even when heterogeneity tests are insignificant. In this paper, we consider some exploratory analysis tools to address this issue. We present three measures derived using the theory of order statistics, which can be used to understand the magnitude and the nature of the variation in treatment effects that can arise merely as an artefact of chance. These measures are not intended to replace a formal test of interaction but instead provide non‐inferential visual aids, which allow comparison of the observed and expected differences between regions or other subgroups and are a useful supplement to a formal test of interaction. We discuss how our methodology differs from recently published methods addressing the same issue. A case study of our approach is presented using data from the Study of Platelet Inhibition and Patient Outcomes (PLATO), which was a large cardiovascular MRCT that has been the subject of controversy in the literature. An R package is available that implements the proposed methods. Copyright © 2014 John Wiley & Sons, Ltd.     

Phase I trial design for drug combinations with Bayesian model averaging

Various statistical models have been proposed for two‐dimensional dose finding in drug‐combination trials. However, it is often a dilemma to decide which model to use when conducting a particular drug‐combination trial. We make a comprehensive comparison of four dose‐finding methods, and for fairness, we apply the same dose‐finding algorithm under the four model structures. Through extensive simulation studies, we compare the operating characteristics of these methods in various practical scenarios. The results show that different models may lead to different design properties and that no single model performs uniformly better in all scenarios. As a result, we propose using Bayesian model averaging to overcome the arbitrariness of the model specification and enhance the robustness of the design. We assign a discrete probability mass to each model as the prior model probability and then estimate the toxicity probabilities of combined doses in the Bayesian model averaging framework. During the trial, we adaptively allocated each new cohort of patients to the most appropriate dose combination by comparing the posterior estimates of the toxicity probabilities with the prespecified toxicity target. The simulation results demonstrate that the Bayesian model averaging approach is robust under various scenarios. Copyright © 2015 John Wiley & Sons, Ltd.     

Notes on estimation of the intraclass correlation under the AB/BA crossover trial

Under the AB/BA crossover trial, we focus our attention on estimation of the intraclass correlation in normal data. We develop both point and interval estimators in closed form for the intraclass correlation. We employ Monte Carlo simulation to study the performance of these estimators in a variety of situations. We note that the estimators developed here for the intraclass correlation remain valid even when there are possibly unexpected carry-over effects.     

审判经验的迷局与研判——从“案多人少”切入

2008年以来,江苏法院开展了大规模的总结审判经验专项活动。这是在案件数量剧增的态势下法院为化解案多人少的矛盾之为,但得到的经验相当一部分并非是有效提升办案效率的＂精品＂。从短期看,审判经验总结会适得其反,加大案多人少压力;但从长期来看,对于缓解案多人少压力会有所帮助。因此,审判经验有总结的价值,但在传承和发展审判经验时,对于个人经验和集体经验应当区别对待。     

中国法学实证研究客观性难题求解——韦伯社会科学方法论的启示

以实证研究方法为特色的中国法治实践学派日益受到关注。中国法学研究方法正处于转型之中,实证研究方法将成为法学研究的常规范式。一些学者对法学实证研究的客观性提出质疑。求解实证研究的客观性难题可以从马克斯·韦伯那里得到启发。韦伯对社会科学的客观性研究具有代表性,认为人文社会科学可以做到“价值无涉”。韦伯主张的客观性以价值关联为前提,以客观可能性为基础,以对理想类型的应用和超越为实现路径。在法学研究中,运用指向客观性的社会科学研究方法具有必然性,这是由法学研究对象的广泛性以及法学对法律的批判功能决定的。法学实证研究并不排斥主流的规范研究,两者应互相补充,这也是中国法治实践学派的基本立场。中国法学实证研究要实现客观性,需要兼顾证实与证伪,注重文献的积累、理解的逻辑以及实践。中国法治实践学派的目标是要在韦伯方法论基础上实现创新和超越。     

The mad estimator: when is it non-linear? applications to two-way design models

The mean absolute deviation (MAD) estimator has recently received a great deal of attention as applied to full-rank linear regression models. This paper provides a necessary and sufficient condition for the MAD estimator to be a non-linear estimator, in which case conditions for the variance of the MAD estimator to be larger or smaller than those for OLS are, in general, unknown. The non-linearity of the MAD estimator is examined for several two-way designs; in particular (1) randomized block design (2) two-way nested design (3) two-way classification with interaction and (4) partially balanced incomplete block design     

■匜铭文集释及西周诬告案件的审理程序窥探

西周时期没有专门的法律条文,■是一篇涉法铭文,其中涉及到的犯罪是诬告罪。本文在对铭文进行集释和翻译的基础上,总结出这次诬告案件的审理程序,这有助于了解西周时期的法律情况。