Implementation of maximin efficient designs in dose‐finding studies

This paper considers the maximin approach for designing clinical studies. A maximin efficient design maximizes the smallest efficiency when compared with a standard design, as the parameters vary in a specified subset of the parameter space. To specify this subset of parameters in a real situation, a four‐step procedure using elicitation based on expert opinions is proposed. Further, we describe why and how we extend the initially chosen subset of parameters to a much larger set in our procedure. By this procedure, the maximin approach becomes feasible for dose‐finding studies. Maximin efficient designs have shown to be numerically difficult to construct. However, a new algorithm, the H‐algorithm, considerably simplifies the construction of these designs. We exemplify the maximin efficient approach by considering a sigmoid Emax model describing a dose–response relationship and compare inferential precision with that obtained when using a uniform design. The design obtained is shown to be at least 15% more efficient than the uniform design. © 2014 The Authors. Pharmaceutical Statistics Published by John Wiley & Sons Ltd.     

Locally and maximin optimal designs for multi-factor nonlinear models

This paper considers the search for locally and maximin optimal designs for multi-factor nonlinear models from optimal designs for sub-models of a lower dimension. In particular, sufficient conditions are given so that maximin D-optimal designs for additive multi-factor nonlinear models can be built from maximin D-optimal designs for their sub-models with a single factor. Some examples of application are models involving exponential decay in several variables.     

Practical approaches for design and analysis of clinical trials of infertility treatments: crossover designs and the Mantel–Haenszel method are recommended

Crossover designs have some advantages over standard clinical trial designs and they are often used in trials evaluating the efficacy of treatments for infertility. However, clinical trials of infertility treatments violate a fundamental condition of crossover designs, because women who become pregnant in the first treatment period are not treated in the second period. In previous research, to deal with this problem, some new designs, such as re‐randomization designs, and analysis methods including the logistic mixture model and the beta‐binomial mixture model were proposed. Although the performance of these designs and methods has previously been evaluated in large‐scale clinical trials with sample sizes of more than 1000 per group, the actual sample sizes of infertility treatment trials are usually around 100 per group. The most appropriate design and analysis for these moderate‐scale clinical trials are currently unclear. In this study, we conducted simulation studies to determine the appropriate design and analysis method of moderate‐scale clinical trials for irreversible endpoints by evaluating the statistical power and bias in the treatment effect estimates. The Mantel–Haenszel method had similar power and bias to the logistic mixture model. The crossover designs had the highest power and the smallest bias. We recommend using a combination of the crossover design and the Mantel–Haenszel method for two‐period, two‐treatment clinical trials with irreversible endpoints. Copyright © 2015 John Wiley & Sons, Ltd.     

D-optimal mixture component-amount designs for quadratic and cubic models

When the total amount of a mixture of ingredients needs to be taken into account (in addition to the composition of its ingredients), an experimental design requires several levels of the amount. Designs for such situations are discussed, and D-optimal choices are made for fitting quadratic and cubic models, for various numbers of experimental units.     

Book Reviews

Books reviewed:
Anthony, Atkinson & Marco, Riani, Robust Diagnostic Regression Analysis
N., Balakrishnan & C.R., Rao, Order Statistics: Theory & Methods. Handbook of Statistics, Volume 16
N., Balakrishnan & C.R., Rao, Order Statistics: Applications. Handbook of Statistics, Volume 17
C.R., Rao & G.J., Székely, Statistics for the 21st Century: Methodologies for Applications of the Future
D.A., Nolan & T.P., Speed, Stat Labs: Mathematical Statistics Through Applications
W.N., Venables & B.D., Ripley, S Programming
Peter W.M., John, Statistical Design and Analysis of Experiments     

Optimal designs for discriminating between some extensions of the Michaelis–Menten model

In this paper some results on the computation of optimal designs for discriminating between nonlinear models are provided. In particular, some typical deviations of the Michaelis–Menten model are considered. A common deviation of this pharmacokinetic model consists on adding a linear term. If two linear models differ in one parameter the T-optimal design for discriminating between them is c-optimal for estimating the added linear term. This is not the case for nonlinear models.     

关于西部高校图书馆收藏和开发藏族图案文献的思考

藏族图案是藏民族最灵动的艺术表现。本文分析了藏族图案文献的特点和社会功能,指出了现代化过程中藏族图案文献的收藏和开发利用工作所面临的挑战。在此基础上,阐述了一些西部高等学校在藏族图案文献的收藏和开发利用方面应承当的社会责任以及需要处理好的几个问题。     

西部大开发与贵州少数民族教育改革和发展

新中国成立50多年来,特别是改革开放和实施西部大开发战略以来,贵州民族教育取得了巨大成就, 初步形成了从学前教育到高等教育在内的民族教育体系,为提高我省少数民族的科学文化素质、促进 少数民族地区经济发展和社会进步、加强民族团结、保持民族地区社会稳定做出了重大贡献。但由于 历史、社会、自然条件,特别是经济发展水平等多种原因,我省民族教育还面临着一些特殊的困难和问 题。为落实中央民族工作会议和全国第五次民族教育工作会议精神,深化改革,加快发展我省民族教 育,我们承担了国家社会科学基金全国教育科学“十五”规划民族教育方面唯一重点课题“西部大开发 与中国少数民族教育改革和发展研究”子课题之一的《西部大开发与贵州少数民族教育改革和发展研 究》,并提出了我们的总体研究思路和设计方案。     

An unexpected meeting of four seemingly unrelated problems: graph testing, DNA complex screening, superimposed codes and secure key distribution

This paper discusses the relation among four problems: graph testing, DNA complex screening, superimposed codes and secure key distribution. We prove a surprising equivalence relation among these four problems, and use this equivalence to improve current results on graph testing. In the rest of this paper, we give a lower bound for the minimum number of tests on DNA complex screening model. The first and second author would like to dedicate this paper to professor Frank K. Hwang on the occasion of his 65th birthday. This research is partially supported by Republic of China, National Science Council grant NSC 92-2115-M-009-014.