Analysis of treatment response data from eligibility designs

In this paper, we develop and compare two alternative approaches for calculating the effect of the actual intake when treatments are randomized, but compliance with the assignment in the treatment arm is less than perfect for reasons that are correlated with the outcome. The approaches are based on different identification assumptions about these unobserved confounders. In the first approach, which stems from [Sommer, A., Zeger, S., 1991. On estimating efficacy in clinical trials. Statistics in Medicine 10, 45–52], the unobserved confounders are modeled by a discrete indicator variable that represents subject-type, defined in terms of the potential intake in the face of each possible assignment. In the second approach, confounding is modeled without reference to subject-type in the spirit of the Roy model. Because the two models are non-nested, and model comparison and assessment of the approaches in a real data setting is one of our central goals, we formulate the discussion from a Bayesian perspective, comparing the two models in terms of marginal likelihoods and Bayes factors, and in terms of inferences about the treatment effects. The latter we calculate from a predictive perspective in a way that is different from that in the literature, where typically only a point summary of that effect is calculated. Our real data analysis focuses on the JOBS II eligibility trial that was implemented to test the effectiveness of a job search seminar in decreasing the negative mental health effects commonly associated with job loss. We provide a comparative analysis of the data from the two approaches with prior distributions that are both reasonable in the context of the data and comparable across the model specifications. We show that the approaches can lead to different evaluations of the treatment.     

浅谈传统图形与现代标志设计的结合

我国传统图形艺术源远流长,其代表着中国几千年的文化内涵,将传统图形与现代标志设计相结合,成为设计的一个新启示和新创意。本文分别从传统图形的溯源,意义以及在现代标志设计中的应用等方面进行阐述。     

大埔变电站—大埔水电站35kV线路融江跨河工程设计综述

文章介绍了35 kV长档柜线路的设计计算过程及要求,为线路工程设计提供有益借鉴。     

On randomization, modeling and experimental design: some remarks on a paper by De Vos

De Vos (1991) claims to have discovered a new example from agricultural field experimentation which shows that a simple robust spatial model may lead to inference and systematic experimental design that outperforms the inference from randomized experiments by far. In this reaction it is shown that: (1) the example is not new; (2) the gains in efficiency are exaggerated due to comparison with an inefficient randomization method; (3) the paper is over-optimistic with respect to robustness of model-based methods and throws unjustified doubts on the validity of randomization methods; (4) the choice between randomization methods and model-based methods depends on the relative importance attached to efficiency and validity.     

Polygonal designs with blocks of size k≤10

The use of polygonal designs is motivated by the desire to avoid the selection of contiguous units in a sample from an ordered finite population. However very little is known about polygonal designs that have block size 5 or more. We present new polygonal designs with blocks of sizes 5 through 10, including the first designs with block sizes 9 and 10. For block sizes 5 through 7, we identify, with one possible exception, all values for the number of varieties for which a polygonal design exists. Received January 2001     

Distance optimality design criterion in linear models

Properties of the most familiar optimality criteria, for example A-, D- and E-optimality, are well known, but the distance optimality criterion has not drawn much attention to date. In this paper properties of the distance optimality criterion for the parameter vector of the classical linear model under normally distributed errors are investigated. DS-optimal designs are derived for first-order polynomial fit models. The matter of how the distance optimality criterion is related to traditional D- and E-optimality criteria is also addressed. Received: June 1999     

A note on the robustness of Box-Behnken designs to the unavailability of data

Box-Behnken designs and central composite designs are efficient designs for fitting second order polynomials to response surfaces, because they use relatively small numbers of observations to estimate the parameters. In this paper we investigate the robustness of Box-Behnken designs to the unavailability of observations, in the sense of finding t _max , the maximum number of arbitrary rows in the design matrix that can be removed and still leave all of the parameters of interest estimable. The results are compared to the known results for the central composite designs found in MacEachern, Notz, Whittinghill & Zhu (1995). The blocked Box-Behnken designs are equally as robust as those that are not blocked. Received December 1997     

Efficiencies of Rounded Optimal Approximate Designs for Small Samples

Optimal exact designs are notoriously hard to study and only a few of them are known for polynomial models. Using recently obtained optimal exact designs (I mhof , 1997), we show that the efficiency of the frequently used rounded optimal approximate designs can be sensitive if the sample size is small. For some criteria, the efficiency of the rounded optimal approximate design can vary by as much as 25% when the sample size is changed by one unit. The paper also discusses lower efficiency bounds and shows that they are sometimes the best possible bounds for the rounded optimal approximate designs.     

物理化学实验改进——液体饱和蒸气压的测定

对传统的物理化学实验之一——液体饱和蒸气压的测定进行五点改进:1、将有毒的苯改成无毒的乙醇;2、将不易读数的水银温度计改成简单易读的数据温度计;3、将水银U形压力计改成DP-A精密数字压力计;4、将普通的缓冲瓶改成不锈钢缓冲储气罐;5、用Excel处理实验数据代替手工作图。如此这些既体现绿色环保又提高实验结果的准确性。     

单层工业厂房中双跨排架结构设计问题——以百乐水电站厂房上部结构设计为例

单层双跨排架是厂房常用的承重形式,文章结合百乐水电站厂房上部结构设计,归纳总结出类似结构的计算方法.