Assessing Effects on Long-term Survival after Early Termination of Randomized Trials

In this paper we present an approach to using historical control data to augment information from a randomized controlled clinical trial, when it is not possible to continue the control regimen to obtain the most reliable and valid assessment of long term treatment effects. Using an adjustment procedure to the historical control data, we investigate a method of estimating the long term survival function for the clinical trial control group and for evaluating the long term treatment effect. The suggested method is simple to interpret, and particularly motivated in clinical trial settings when ethical considerations preclude the long term follow-up of placebo controls. A simulation study reveals that the bias in parameter estimates that arises in the setting of group sequential monitoring will be attenuated when long term historical control information is used in the proposed manner. Data from the first and second National Wilms' Tumor studies are used to illustrate the method.     

Homogeneity of Two Straight Lines: Equivalence Approach Using Fitted Regressions

The paper examines the homogeneity of a pair of straight lines, regarded as the expected values of two different linear regressions, from an equivalence point of view. This seems more appropriate than the usual testing of the null hypothesis of homogeneity when the aim is to establish that the lines are close to homogeneous. Upper confidence bounds on the maximum difference between the lines are based on the usual least squares regression estimators, assuming normal distributions. These bounds are constructed for fixed points, or over a fixed interval, and it is concluded that the lines are 1-homogeneous if the bounds are not greater than 1: Also, intervals are constructed over which the lines are concluded to be 1-homogeneous.     

A Characterization of the Normal Family of Distributions Based on the Bias of the Maximum Likelihood Estimator

This paper characterizes the family of Normal distributions within the class of exponential families of distributions, via the structure of the bias of the maximum likelihood estimator Θ _n of the canonical parameter Θ . More specifically, when E _θ ( Θ n ) – Θ = (1/ n ) Q ( Θ ) + o (1/ n ), the equality Q ( Θ ) = 0 proves to be a property of the Normal distribution only. The same conclusion is obtained for the one-dimensional case bt assuming that Q ( Θ ) is a polynomial of Θ .     

A Goodness-of-fit Test for Exponentiality Based on the Memoryless Property

In this investigation a test of goodness of fit for exponentiality is proposed. This procedure applies equally whether the scale and/or the location parameters of the distribution are known or not. The limiting null and non-null distributions of the test statistic are normal under minimal conditions. Monte Carlo critical values for small sample sizes are given and the power of the test is calculated for various alternatives showing that it compares favourably relatively to other more complicated published procedures.     

A modified Kolmogorov-Smirnov test for a rectangular distribution with unknown parameters: Computation of the distribution of the test statistic

A recursive scheme for the calculation of the distribution of the test statistic of a modified Kolmogorov-Smirnov-test for a rectangular distribution with unknown parameters is given.     

晋西三川河流域的地表组成物质及其与土壤侵蚀的关系

地表组成物质是影响三川河流域土壤侵蚀及滑坡发育的重要因素。本文在分析该流域的地表组成物质的类型、性质及分布规律的基础上,探讨了地表组成物质与土侵馒蚀的关系。     

球墨铸铁曲轴的气体软氮化

柴油机的珠墨铸铁曲轴系重要零件,气体软氮化应用到球墨铸铁领域还是一种新工艺,而且比中频淬火效果好,提高了曲轴的抗疲劳和抗磨损的能力。本文对气体软氮化的基本原理、设备、工艺参数的选择和催渗方法进行了探讨,对软氮化后曲轴的尺寸形状误差、光洁度和机械性能的提高等进行了较详细的试验、分析和比较,结果,经气体软氮化后的曲轴不但尺寸形站误差符合图纸要求外,而且抛去轻微氧化层后光洁度还略有提高,曲轴安全系数由1.3～1.6提高到1.70～1.77,并且一般不再发生疲劳断(?),使用寿命比原来寿命增加3.32倍以上。     

广州师范学院教师师德状况的调查

本文分析了广州师范学院教师的师德状况,并针对教师师德状况和师德建设中存在的问题,提出加强教师师德建设的建议和意见。     

加强师德建设 提高师德修养

本文认为加强师德建设,一方面要着重搞好职业理想宣传教育,加强领导作风建设,以及从严治教,测评量化管理;另一方面在于师德修养,坚定师德信念,坚持理论与实践相结合,以及自我教育、自我完善。     

对跨世纪广州师范学院教师队伍建设的若干看法

本文论述跨世纪教师队伍建设的重大战略意义并针对广州师范学院的某些实际情况,提出抓好跨世纪教师队伍建设的若干对策。