Three-stage designs for monitoring clinical trials

Optimal three-stage designs with equal sample sizes at each stage are presented and compared to fixed sample designs, fully sequential designs, designs restricted to use the fixed sample critical value at the final stage, and to modifications of other group sequential designs previously proposed in the literature. Typically, the greatest savings realized with interim analyses are obtained by the first interim look. More than 50% of the savings possible with a fully sequential design can be realized with a simple two-stage design. Three-stage designs can realize as much as 75% of the possible savings. Without much loss in efficiency, the designs can be modified so that the critical value at the final stage equals the usual fixed sample value while maintaining the overall level of significance, alleviating some potential confusion should a final stage be necessary. Some common group sequential designs, modified to allow early acceptance of the null hypothesis, are shown to be nearly optimal in some settings while performing poorly in others. An example is given to illustrate the use of several three-stage plans in the design of clinical trials.     

Group sequential x2 statistic for testing the difference of two mean vectors in clinical trials

In this study we discuss the group sequential procedures for comparing two treatments based on multivariate observations in clinical trials. Also we suppose that a response vector on each of two treatments has a multivariate normal distribution with unknown covariance matrix. Then we propose a group sequential x² statistic in order to carry out repeated significance test for hypothesis of no difference between two population mean vectors. In order to realize the group sequential test where average sample number is reduced, we propose another modified group sequential x² statistic by extension of Jennison and Turnbull ( 1991 ). After construction of repeated confidence boundaries for making the repeated significance test, we compare two group sequential procedures based on two statistics regarding the average sample number and the power of the test in the simulations.     

A two-sample parametric group sequential procedure for monitoring clinical trials

A group sequential procedure is presented which allows for staggered entry of patients, random loss to followup, and utilizes the flexible boundary approach of Lan and DeMets. The proposed procedure assumes that response times are nearly exponentially distributed. An example as well as simulation studies comparing the performance of the proposed procedure with the group sequential logrank are also presented.     

美国公司背景下的律师—委托人特免权适用标准研究

为了促进委托人和律师充分且深入地交流一切案件信息,委托人与律师之间的交流内容受到律师—委托人特免权的保护。由公司享有的律师—委托人特免权的适用标准存在很大争议。由公司享有的律师—委托人特免权的适用标准存在普遍适用标准、控制群体标准、事项标准以及其他标准。事项标准与控制群体标准相比扩大了受律师—委托人特免权保护的员工的范围。美国联邦最高法院通过厄普约翰案对由公司享有的律师—委托人特免权的适用标准作出了判决。厄普约翰案为由公司享有适用律师—委托人特免权奠定了基础,但是该判决并未彻底解决适用标准存在的争议。     

仡佬族独特审美意识的历史与自然成因

仡佬族在与恶劣的自然环境抗争和与复杂的社会环境适应的过程中形成了以崇尚生命和追求和谐为特征的审美意识。寻析其特定的审美意识成因和内蕴,可以深刻了解其质朴顽强、包容坚忍的民族精神,及其以弱适强、守护自我的民族性。这可以为在全球化背景中如何应对强势文化冲击提供一点启示。     

对存续企业退出的探讨

存续企业是国有集团公司中未上市部分.在改革进入攻坚阶段,存续企业的改革至关重要.依据非自由退出模型,存续企业的退出选择面临障碍,负外部性大、成本大.因此着眼于存续企业的存续,谋求整个集团公司的协调发展才是改革的较好选择.     

有时间的人--云南孟定傣德的生日、人名与人观

本文拟通过叙述和分析孟定傣德个体人的生日和名字现象,使他们的世界中存在于人体内外的时间得以略见一斑。孟定傣德每一个人的一生中都会有许多名字,随着生命历程的时间之流,以及相对比较共时性的语境变化,人的名字也在迁流:产生、搁置、唤起、更换、累积、遗失、死亡、再生。这种迁流通过与生日、出生顺序等等时间现象的直接联系,通过生日、名字与健康、文化性别(gender)、知识、社会地位等状况的纠缠,塑造着一种有时间的人。     

基于差异教学的小组合作学习分组研究

小组合作学习是一种重要的教学方式,本文将差异教学思想引入小组合作学习,以学生差异为出发点,从学习成绩、智能类型、性别差异三方面,对如何进行更为合理的教学分组进行了探讨。     

浅析集团公司财务管理重点问题

对于集团公司财务管理,为了实现集团总价值最大化的目标,重点在于解决三个问题:一是经营战略上专业化与多元化的协调;二是财务控制中的集权与分权的权衡;三是决策的程序化与灵活性。     

解读满族服饰习俗的文化内涵

满族服饰是满族文化的一种特殊载体,是满族在特定的地域环境和社会环境中,基于对自身生产、生活方式的理解与适应,以及在对精神世界的追求中形成的,具有浓郁的地域特征、独特的审美情趣和丰富的文化内涵。本文通过对满族服饰的进一步剖析,帮助人们真正了解满族传统服饰习俗,把握其世代传承发展的历史规律。