IV估计框架下模型设定检验问题的讨论

 IV估计框架下各种统计量的良好性质依赖于相应的模型设定,如果这些模型设定未能得到数据的支持,其统计推断结论将是不可靠的。如判定计量经济模型是否存在内生性的Hausman检验,实证研究中同一问题的检验结果可能大相径庭。如何通过合理的模型设定检验程序来获得模型参数科学、可靠的估计结果和检验结论呢？本文讨论了工具变量估计框架下的各种模型设定检验问题,明确了各个检验统计量的适用条件及其逻辑联系,给出了工具变量估计框架下模型设定检验的一般步骤。     

Using plausible values in secondary analysis in large-scale assessments

Plausible values are typically used in large-scale assessment studies, in particular, in the Trends in International Mathematics and Science Study and the Programme for International Student Assessment. Despite its large spread, there are still some questions regarding the use of plausible values and how such use affects statistical analyses. The aim of this paper is to demonstrate the role of plausible values in large-scale assessment surveys when multilevel modeling is used. Different user strategies concerning plausible values for multilevel models as well as means and variances are examined. The results show that some commonly used user strategies give incorrect results while others give reasonable estimates but incorrect standard errors. These findings are important for anyone wishing to make secondary analyses of large-scale assessment data, especially those interested in using multilevel models to analyze the data.     

Designing of variables quick switching sampling system by considering process loss functions

This paper proposes a variables quick switching system where the quality characteristic of interest follows a normal distribution and the quality characteristic is evaluated through a process loss function. Most of the variables sampling plans available in the literature focus only on the fraction non-conforming and those plans do not distinguish between the products that fall within the specification limits. The products that fall within specification limits may not be good if their mean is too away from the target value. So developing a sampling plan by considering process loss is inevitable in these situations. Based on this idea, we develop a variables quick switching system based on the process loss function for the application of the processes requiring low process loss. Tables are also constructed for the selection of parameters of variables quick switching system for given acceptable quality level and limiting quality level. The results are explained with examples.     

信息时代语言文字规范与标准问题

制定语言文字规范与标准是当今时代的要求,国家利益的需要。目前已有的规范与标准远远不能满足社会对语言文字规范、标准的需求。无论是硬标准还是软标准,都面临着严峻的国际挑战。缺乏科学的标准,导致我们的汉语教材和语文教材缺乏科学性。为了国家的利益,为了祖国的安全,为了构建和谐的语言生活,要加速基础研究,要加速研究、制定有关语言文字的各项规范与标准。     

A generalized least squares estimation method for VARMA models

In this paper a new generalized least squares procedure for estimating VARMA models is proposed. This method differs from existing ones in explicitly considering the stochastic structure of the approximation error that arises when lagged innovations are replaced with lagged residuals obtained from a long VAR. Simulation results indicate that this method performs better than the Double Regression method and similar to Mauricio's (1995) exact maximum likelihood estimation procedure.     

双语服务——大学图书馆的新选择

“双语服务”对大学图书馆的服务创新具有重要意义。图书馆实现双语服务,应该在环境视觉感官双语对照、日常接待礼仪用语、馆藏建设资源保障、参考咨询工作服务、人力资源管理、团队外语素质目标等方面的双语服务进行全面的设计与实施,以提升大学图书馆的信息服务水平。     

Determining the Optimum Process Mean of a One-sided Specification Limit with the Linear Quality Loss Function of Product

Wen & Mergen (1999) proposed a method for setting the optimal process mean when a process was not capable of meeting specifications in the short term. However, they neglected to consider the quality loss for a product within specifications in the model. Chen & Chou (2002) presented a modified Wen & Mergen's (1999) model, including the quadratic quality loss function for a one-sided specification limit. In this paper, we propose the modified Wen & Mergen (1999) cost model including the linear quality loss function of a product for determining the optimal process mean of a one-sided specification limit.     

Immigrant children in the age of educational reform

Abstract

Immigrant children are the fastest growing subgroup among United States schoolchildren today. This paper explores how the new testing movement affects these students, many of which are English language learners.The passage of new federal laws mandating that all students be tested within one year of entrance into a U.S. school is refuted by long standing research. Studies have demonstrated that it takes five to seven years for students to attain the academic language necessary to achieve success in educational settings.This paper explores the instructional program options for immigrant students and advocates for changes in the current testing protocol for them.     

Exact solutions to the Behrens–Fisher Problem: Asymptotically optimal and finite sample efficient choice among

The problem of testing the equality of two normal means when variances are not known is called the Behrens–Fisher Problem. This problem has three known exact solutions, due, respectively, to Chapman, to Prokof’yev and Shishkin, and to Dudewicz and Ahmed. Each procedure has level alpha and power beta when the means differ by a given amount delta, both set by the experimenter. No single-sample statistical procedures can make this guarantee. The most recent of the three procedures, that of Dudewicz and Ahmed, is asymptotically optimal. We review the procedures, and then compare them with respect to both asymptotic efficiency and also (using simulation) in finite samples. Of these exact procedures, based on finite-sample comparisons the Dudewicz–Ahmed procedure is recommended for practical use.