On the maximum number of constraints for s-symbol balanced arrays of strength t

Several upper bounds on the maximum number of constraints for s-symbol balanced arrays of strength t are given. Some bounds derived here include the results obtained by Rafter and Seiden (1974), Chopra (1982, 1983) and Saha, Mukerjee and Kageyama (1983).     

On a bayesian approach for the shiftpoint problem

Using a direct resampling process, a Bayesian approach is developed for the analysis of the shiftpoint problem. In many problems it is straight forward to isolate the marginal posterior distribution of the shift-point parameter and the conditional distribution of some of the parameters given the shift point and the other remaining parameters. When this is possible, a direct sampling approach is easily implemented whereby standard random number generators can be used to generate samples from the joint posterior distribution of aii the parameters in the model. This technique is illustrated with examples involving one shift for Poisson processes and regression models.     

Quotas on runs of successes and failures in a multi-state markov chain

For the time-homogeneous multi-state Markov chain {X_n,n≧0} with states labeled as "0" (success) and "f"(failure), f=1,2,… the waiting time problems to be discussed arise by setting quotas on runs of success and failures. Some particular cases are considered.     

Covariate classification by post–stratification

The plug–in Anderson's covariate classification statistic is constructed on the basis of an initially unclassified training sample by means of posty–stratification. The asymptotic efficiency relative to the discriminant based on an initially classified training sample is evaluated for the case where a covariate is present. Effect of post–stratification is examined.     

Quadratic perturbation expansions of certain functions of eigenvalues and eigenvectors and their application to sensitivity analysis in multivariate methods

Tanaka (1988) lias derived the influence functions, which are equivalent to the perturbation expansions up to linear terms, of two functions of eigenvalues and eigenvectors of a real symmetric matrix, and applied them to principal component analysis. The present paper deals with the perturbation expansions up to quadratic terms of the same functions and discusses their application to sensitivity analysis in multivariate methods, in particular, principal component analysis and principal factor analysis. Numerical examples are given to show how the approximation improves with the quadratic terms.     

Consultants' forum: should post hoc sample size calculations be done?

Pre‐study sample size calculations for clinical trial research protocols are now mandatory. When an investigator is designing a study to compare the outcomes of an intervention, an essential step is the calculation of sample sizes that will allow a reasonable chance (power) of detecting a pre‐determined difference (effect size) in the outcome variable, at a given level of statistical significance. Frequently studies will recruit fewer patients than the initial pre‐study sample size calculation suggested. Investigators are faced with the fact that their study may be inadequately powered to detect the pre‐specified treatment effect and the statistical analysis of the collected outcome data may or may not report a statistically significant result. If the data produces a “non‐statistically significant result” then investigators are frequently tempted to ask the question “Given the actual final study size, what is the power of the study, now, to detect a treatment effect or difference?” The aim of this article is to debate whether or not it is desirable to answer this question and to undertake a power calculation, after the data have been collected and analysed. Copyright © 2008 John Wiley & Sons, Ltd.     

优化国际语言服务环境背景下关于大学英语写作教学的若干反思

国际语言服务的水平直接体现了一个城市乃至国家的国际化程度,关系到一个城市或国家的国际形象和国际竞争力。随着中国与国际社会的交流日深,对既有自己的专业又具备一定的英语综合运用能力的复合型人才的需求也随之增加。他们不但要有一定的英语口头表达能力,书面表达能力也面临着新的挑战和要求。但我国高校的大学英语课普遍对写作环节重视不足,导致学生的写作基础薄弱。文章分析了大学英语写作过程中存在的普遍性问题并提出了相应的对策。     

多媒体外语教学中的问题及对策

随着现代化科学技术的发展 ,多媒体教学作为现代教育技术不断地介入外语教学中 ,然而 ,在外语教学实践中发现 ,教师对软件 课件多媒体的使用等方面还存在着一些需要探讨的问题。为了更好地发挥多媒体在外语教学中的作用 ,笔者针对在教学实践中发现的一些问题作一探讨 ,并提出相应的措施和建议     

西部开发的问题与模式

本文剖析了西部开发的国内外背景、具备的优势和面临的各种问题,对比分析了国内外地区发展和解决地区经济不平衡问题的十个模式,提出了西部开发的十项建议。     

一阶非线性常微分方程的极值解

本文利用上下解方法和不动点理论研究一阶非线性常微分方程的极值解,改进和推广了现有结果。