Conditional interval estimation of the mean following rejection of a two sided test

The effect of rejecting a two-sided preliminary test of significance for the mean of a normal distribution upon subsequent interval estimation of the mean is examined. For the case where the variance is known, conditional confidence intervals may be shorter than unconditional intervals, in contrast to the one-sided preliminary test case examined by Meeks and D’Agostino (1983, The American Statistician, 7, 134-136) . For the case where the variance is unknown and must be estimated by the sample variance, it is shown that customary intervals do not offer uniformly greater or lesser coverage than the nominal level.     

参数假设检验教学中的几个问题

在概率统计教学的基础上,对参数假设检验教学中出现的学生难于理解的几个问题做了系统的总结,主要包括决策的依据,拒绝域的选择以及决策可靠性的判断,其中对做出"接受零假设"决策的可靠性给出了解释。     

Robust pairwise multiple comparisons under short-tailed symmetric distributions

In one-way ANOVA, most of the pairwise multiple comparison procedures depend on normality assumption of errors. In practice, errors have non-normal distributions so frequently. Therefore, it is very important to develop robust estimators of location and the associated variance under non-normality. In this paper, we consider the estimation of one-way ANOVA model parameters to make pairwise multiple comparisons under short-tailed symmetric (STS) distribution. The classical least squares method is neither efficient nor robust and maximum likelihood estimation technique is problematic in this situation. Modified maximum likelihood (MML) estimation technique gives the opportunity to estimate model parameters in closed forms under non-normal distributions. Hence, the use of MML estimators in the test statistic is proposed for pairwise multiple comparisons under STS distribution. The efficiency and power comparisons of the test statistic based on sample mean, trimmed mean, wave and MML estimators are given and the robustness of the test obtained using these estimators under plausible alternatives and inlier model are examined. It is demonstrated that the test statistic based on MML estimators is efficient and robust and the corresponding test is more powerful and having smallest Type I error.     

On False Discovery and Non‐discovery Proportions of the Dynamic Adaptive Procedure

This paper studies the asymptotic behaviour of the false discovery and non‐discovery proportions of the dynamic adaptive procedure under some dependence structure. A Bahadur‐type representation of the cut point in simultaneously performing a large scale of tests is presented. The asymptotic bias decompositions of the false discovery and non‐discovery proportions are given under some dependence structure. In addition to existing literatures, we find that the randomness due to the dynamic selection of the tuning parameter in estimating the true null rate serves as a source of the approximation error in the Bahadur representation and enters into the asymptotic bias term of the false discovery proportion and those of the false non‐discovery proportion. The theory explains to some extent why some seemingly attractive dynamic adaptive procedures do not outperform the competing fixed adaptive procedures substantially in some situations. Simulations justify our theory and findings.     

无机化学实验教学改革探索

分析了高校化工、生物技术、环境保护及食品工程等相关专业的专业基础课程《无机化学》实验教学改革的必要性,探索并实施了一系列有效的改革方案,取得了良好的实验教学效果.     

大学英语听力测试及应试技巧

听是四大语言技能中十分重要,但又难以掌握的一种技能。听解过程实际上是个信息加工过程,它受到诸如受试的语言知识、非语言知识及记忆力等诸方面的影响。可从听解的实质出发,分析影响听解的因素及如何采取一些有效应试技巧以求指导考生在CET4-6级中发挥最好水平。     

2000m~3二甲醚球罐的在线检测及有限元分析

首先,使用多通道声发射检测仪PAC SAMOS-48检测在用2000m3二甲醚球形储罐,判定出该设备存在表面裂纹缺陷及其所处位置。然后,采用超声波检测方法,确定了裂纹形状和大小。用Newman—Raju方法研究了表征裂纹缺陷前沿应力场以及位移场的重要参量即应力强度因子,并利用ANSYS建立简化的有限元模型,最终得到裂纹的应力云图和该裂纹前沿应力强度因子值,与工程估算方法得到的数值进行对比,结果表明有限元方法应用于压力容器缺陷的分析是适用的。     

Statistical analysis of a two-unit dependent repairable system

Maximum likelihood estimators are investigated a for lr-out-of 2:G repairable system when failures and repairs are statistically dependent. Under two censoring schemes Accelerated Life Testing Procedure (ALTP) is used to obtain the estimates. Information matrices are supplied and a special case when the failure and repair phenomenon are independent of each other is considered.     

How to Teach by the Unit Method

Using data from the National Center for Educational Statistics research spanning fifteen years, researchers examined the impact of national educational policy implementation on the role of social studies in elementary schools. Specifically, with the reauthorization of No Child Left Behind (NCLB) in 2007 and the continuation of federal-mandated testing of English language arts (ELA) and mathematics in grades three through five, researchers sought to understand how policy decisions to extend testing to science affected teacher decisions in regard to instructional time allocations for core subject areas of ELA, mathematics, science, and social studies in elementary schools. Results of this quantitative study offer large-scale evidence of the declining role of social studies in an era in which testing is clearly linked to subject-area importance. Findings provide an overview of the national scope of testing and the ramifications for social studies in elementary schools. Researchers conclude that curriculum standardization, accountability, and high-stakes testing have had adverse affects on social studies time allotments in comparison to tested subjects.