Discreteness Causes Bias in Percentage-Based Comparisons: A Case Study From Educational Testing

Discretizing continuous distributions can lead to bias in parameter estimates. We present a case study from educational testing that illustrates dramatic consequences of discreteness when discretizing partitions differ across distributions. The percentage of test takers who score above a certain cutoff score (percent above cutoff, or “PAC”) often describes overall performance on a test. Year-over-year changes in PAC, or ΔPAC, have gained prominence under recent U.S. education policies, with public schools facing sanctions if they fail to meet PAC targets. In this article, we describe how test score distributions act as continuous distributions that are discretized inconsistently over time. We show that this can propagate considerable bias to PAC trends, where positive ΔPACs appear negative, and vice versa, for a substantial number of actual tests. A simple model shows that this bias applies to any comparison of PAC statistics in which values for one distribution are discretized differently from values for the other.     

A Goodness-of-fit Test for Exponentiality Based on the Memoryless Property

In this investigation a test of goodness of fit for exponentiality is proposed. This procedure applies equally whether the scale and/or the location parameters of the distribution are known or not. The limiting null and non-null distributions of the test statistic are normal under minimal conditions. Monte Carlo critical values for small sample sizes are given and the power of the test is calculated for various alternatives showing that it compares favourably relatively to other more complicated published procedures.     

大学英语四、六级网络考试考场建设研究

大学英语四、六级网考项目开始于2007年,第一次四级网考试点工作实施于2008年12月。大学英语四、六级网考项目的建设目标,是提高大学英语四、六级考试的效度和考务管理效率。以2009年10月份的一次考试为例,描述CET-4大学英语网考考场内的硬件设置、环境设置、网考所需的软件、硬件配置和考试系统的操作流程,并且对网考中出现的问题进行剖析,有助于提出行之有效的改进方案。     

产城协同度测评体系的构建及应用

产城协同发展是走新型城镇化道路,实现区域经济可持续、低成本发展的关键。产业与城市发展之间存在着非线性耦合关系,以此可构建产城协同度测评体系,体系由测量模型、指标体系、指标权重三部分构成。该测评体系可以在很大程度上量化反映出区域产城协同的状况,但测评效度还有待提高。以四川省攀枝花市为例,利用该体系实证测量表明,2004—2011年间,该市产业与城市的发展处于良好协同状态,产城相互支撑发展状况良好。     

Some subjective bayesian considerations in the selection of models

Some considerations relating to the post-data selection of models are discussed. These include some difficulties with orthodox theory, implementation of the likelihood principle, and Bayesian tests of hypotheses.     

A differencing test

This paper proposes and applies a test procedure for misspecification in a dynamic regression model with moving average errors. The test statistics are based on testing for unit roots in the moving average process when the model is deliberately overdifferenced.     

An adaptive estimatcr frequently used in material fatigue testing

Small sample sizes in material fatigue tests give rise to an adaptive estimator of the 100(1-P)% normal percentile, which is the 100P% survival load. The mean squared relative efficiency of the best invariant estimator of normal percentiles to the adaptive estimator is dependent upon the unknown parameters only through the coefficient of variation. The adaptive estimator is shown to be more locally efficient than tl-:ebest invariant estimator over a subset of the parameter space. However, in the extreme values of P the coverage probabilities of the adaptive estimator provide little more protection than a traditional point estimator over the range of preference based on mean squared relative efficiency.     

An introduction to econometric applications of empirical process theory for dependent random variables

This paper discusses some uses in econometrics of empirical process theory for dependent rendom variables. Examples considered include non-standard parametric hypotheses tests and semiparametric estimation. The application of bracketing functional limit results is discussed in some detail     

论TBLA对商务英语口语测试的启示

基于任务的语言测试(TBLA)作为一种新的语言测试模式,成为了研究热点.口语测试作为语言测试不可或缺的一部分,在强调交际语言教学的今天越来越受到人们的关注.口语测试目标的确定、测试任务的选择和设计以及测试效度的验证是进行基于任务的商务英语口语测试所要研究的主要问题.     

Computer Use in Psychometric Assessment

The expansion of computer technology has created many possibilities for computer applications in the area of psychological testing and assessment. Test taking, scoring, and report writing can all be done with the assistance of computer technology. Although applying new technology in psychometric assessment can reduce costs to agencies and clients, make better use of professional time, and assist in delivering better services to clients, there are also some potential problems that need to be considered. This article evaluates the ways that computers can be used in psychometric assessment, points out the benefits of such use, and considers problems tha may be encountered with these uses.