One and two sample confidence intervals for estimating the mean of skewed populations: an empirical comparative study

In this paper we consider and propose some confidence intervals for estimating the mean or difference of means of skewed populations. We extend the median t interval to the two sample problem. Further, we suggest using the bootstrap to find the critical points for use in the calculation of median t intervals. A simulation study has been made to compare the performance of the intervals and a real life example has been considered to illustrate the application of the methods.     

Improved hypothesis testing in a general multivariate elliptical model

This paper investigates improved testing inferences under a general multivariate elliptical regression model. The model is very flexible in terms of the specification of the mean vector and the dispersion matrix, and of the choice of the error distribution. The error terms are allowed to follow a multivariate distribution in the class of the elliptical distributions, which has the multivariate normal and Student-t distributions as special cases. We obtain Skovgaard's adjusted likelihood ratio (LR) statistics and Barndorff-Nielsen's adjusted signed LR statistics and we compare the methods through simulations. The simulations suggest that the proposed tests display superior finite sample behaviour as compared to the standard tests. Two applications are presented in order to illustrate the methods.     

A powerful test for Balaam's design

The crossover trial design (AB/BA design) is often used to compare the effects of two treatments in medical science because it performs within‐subject comparisons, which increase the precision of a treatment effect (i.e., a between‐treatment difference). However, the AB/BA design cannot be applied in the presence of carryover effects and/or treatments‐by‐period interaction. In such cases, Balaam's design is a more suitable choice. Unlike the AB/BA design, Balaam's design inflates the variance of an estimate of the treatment effect, thereby reducing the statistical power of tests. This is a serious drawback of the design. Although the variance of parameter estimators in Balaam's design has been extensively studied, the estimators of the treatment effect to improve the inference have received little attention. If the estimate of the treatment effect is obtained by solving the mixed model equations, the AA and BB sequences are excluded from the estimation process. In this study, we develop a new estimator of the treatment effect and a new test statistic using the estimator. The aim is to improve the statistical inference in Balaam's design. Simulation studies indicate that the type I error of the proposed test is well controlled, and that the test is more powerful and has more suitable characteristics than other existing tests when interactions are substantial. The proposed test is also applied to analyze a real dataset. Copyright © 2015 John Wiley & Sons, Ltd.     

相似变换下幂零矩阵的{2,3}-逆的表示式

研究复数域上n阶幂零矩阵在相似变换下的{2,3}-逆,运用矩阵块计算方法及Toeplitz矩阵的性质,证明了基于这个幂零矩阵的{2,3}-逆的主要定理,并利用Toeplitz矩阵刻划了幂零矩阵A在相似变换下的所有{2,3}-逆的表达形式.     

高校学习贯彻十六大精神要突出主题

高校学习贯彻落实十六大精神 ,应把握重点、突出主题 ,紧密结合高校实际 ,搞好落实 ,重点解决好高举邓小平理论伟大旗帜 ,贯彻“三个代表”重要思想 ,坚定走有中国特色社会主义道路的信念 ,服务全面建设小康社会的奋斗目标的实现 ,培育社会主义事业的建设者和接班人     

农村劳动力转移与农民收入增长关系的探讨

供给理论是西方经济学的基本理论，本文把这一经济学的基本理论结合中国现阶段实际，阐述了限制农产品产量不能增加中国农民收入，只有转移农村劳动力，在转移劳动力中，发展区域优势行业、畜牧、水产养殖业，加大劳动力输出力度，加快小城镇建设，发展乡镇企业，提高乡镇企业的效益，才能使中国农民增收。     

论“音近”异形词

《第一批异形词整理表》未涉及音近异形词。音近异形词问题似乎是一个无人发表过比较系统的看法的难题。语言事实证明普通话中确实存在着读音相近的异形词,异形词的音近都是由音同转化而来的,它可以从口语音变、古今音变、方言音变中找到同音的根据,还可以从外语中找到音同的根据。解决异形词音近问题应以语音事实为根据。只要能找到音同的根据,便可纳入异形词规范范围。     

青年教师队伍的现状分析及对策

青年教师是高等学校教师队伍的主体,在市场经济大潮冲击下,青年教师队伍存在学历层次偏低、学缘结构不合理、年轻学者缺乏、专业素质不高等问题.笔者试图提出通过结合学校发展战略,狠抓师资规划落实,加强学科建设,培养创新人才等六项措施来加强青年教师队伍建设.     

我国生态公益林补偿的法律制度构造及实施机制创新 ——兼析广东省相关政策与立法实践

建立森林生态效益补偿制度,是实现森林生态价值,发挥森林作为生态环境建设主体作用的必然选择。 我国的生态公益林补偿制度经历了一个从政策调整到国家立法调整以及地方立法试点的渐进过程。但相关的政策法律机制仍存在需要解决的问题,特别是合理设计生态公益林效益补偿的投入与利益保障机制,是关系到能否全面推进生态公益林建设的关键。该文通过分析现有公益林补偿政策立法的现状,结合广东的相关实践情况,提出我国生态公益林补偿的法律制度的创新设计思路。     

Comparison of sample size formulae for 2 × 2 cross‐over designs applied to bioequivalence studies

We consider the comparison of two formulations in terms of average bioequivalence using the 2 × 2 cross‐over design. In a bioequivalence study, the primary outcome is a pharmacokinetic measure, such as the area under the plasma concentration by time curve, which is usually assumed to have a lognormal distribution. The criterion typically used for claiming bioequivalence is that the 90% confidence interval for the ratio of the means should lie within the interval (0.80, 1.25), or equivalently the 90% confidence interval for the differences in the means on the natural log scale should be within the interval (?0.2231, 0.2231). We compare the gold standard method for calculation of the sample size based on the non‐central t distribution with those based on the central t and normal distributions. In practice, the differences between the various approaches are likely to be small. Further approximations to the power function are sometimes used to simplify the calculations. These approximations should be used with caution, because the sample size required for a desirable level of power might be under‐ or overestimated compared to the gold standard method. However, in some situations the approximate methods produce very similar sample sizes to the gold standard method. Copyright © 2005 John Wiley & Sons, Ltd.