A comparative simulation study of the small sample powers of several goodness fit test

Eight goodness of fit tests are compared with respect to their simulated small sample power of detecting an inbreeding alternative to the Hardy-Weinberg null hypothesis. The Pearson's x ² test is found to be most powerful, and the small rample levels of this test are close to the nominal (x ²) significance levels. The use of conditional expectations, rather than expected frequencies based on ML estimates, increases the power and improves thc x ² fit to the true significance level. The small sample powers are also compared to the asymptotic (Pitman) pourer, based on the noncenlral x ² distribution.     

关于COOK算例的数值解

COOK算例没有理论解,文献中常用的参考解与大量优秀单元的计算解有较明显差别,影响了对单元性能的客观公正评价。为获得更准确、更可靠的计算解,分别用4-40次高次元和Q8、T6、QM6低次元进行逼近,考察算例的有限元渐进收敛解。结果表明,在5位有效数字下该问题的解为vC=23.967,σAmax=0.23687,σBmax=-0.20352。     

基于数据驱动平滑检验的密度预测评估方法——以香港恒生指数、上证综指和台湾加权指数为例

本文提出了样本内和样本外密度预测评估的数据驱动平滑检验（data-driven smooth test）方法，并分别采用Newey-Tauchen的方法以及West-McCracken的方法来纠正参数估计对样本内和样本外密度预测评估的影响。运用本文提出的检验方法，我们比较了各种最大熵GARCH模型对中国三个股指数据（香港恒生指数、上证综合指数和台湾加权指数）的样本内和样本外预测绩效。结果显示：（1）最大熵GARCH模型可以用来刻画中国股指数据的典型化事实，GARCH模型中考虑了厚尾和偏态特征的Pearson IV分布对中国股指收益率的样本外预测绩效是很重要的；（2）具有较好样本内拟合优度和样本内预测效果的模型未必有很好的样本外密度预测效果，考虑到样本外预测的重要性，实际应用中我们应采用具有较好样本外预测效果的模型。     

网络自主学习领域研究中的问题

大学英语的网络自主学习正在各个高校广泛开展，对于网络自主学习进行研究也是为了更好地促进学生自主学习的发展，但对该领域的研究存在一些问题，如论文的理论框架部分较少引用最新理论，某些实验研究中存在逻辑缺失之处，即不同实验组别之间没有同等的实验条件，这都会对研究得到正确结论产生不利影响。此外，在实验设计中一些研究过于注重比较学生的成绩等，而这些并不是国家推行网络自主学习的目的所在。网络自主学习的目的是为了促进学生自主学习能力的发展，从某种程度上说，自主学习本身就是目的，因此，不应该用成绩来苛求网络自主学习。衡量网络自主学习是否成功，用质的方法更为合适。     

Planning sequential constant-stress accelerated life tests with stepwise loaded auxiliary acceleration factor

This article presents a design approach for sequential constant-stress accelerated life tests (ALT) with an auxiliary acceleration factor (AAF). The use of an AAF, if it exists, is to further amplify the failure probability of highly reliability testing items at low stress levels while maintaining an acceptable degree of extrapolation for reliability inference. Based on a Bayesian design criterion, the optimal plan optimizes the sample allocation, stress combination, as well as the loading profile of the AAF. In particular, a step-stress loading profile based on an appropriate cumulative exposure (CE) model is chosen for the AAF such that the initial auxiliary stress will not be too harsh. A case study, providing the motivation and practical importance of our study, is presented to illustrate the proposed planning approach.     

Positive quadrant dependence tests for copulas

In this paper the interest is in testing the null hypothesis of positive quadrant dependence (PQD) between two random variables. Such a testing problem is important since prior knowledge of PQD is a qualitative restriction that should be taken into account in further statistical analysis, for example, when choosing an appropriate copula function to model the dependence structure. The key methodology of the proposed testing procedures consists of evaluating a “distance” between a nonparametric estimator of a copula and the independence copula, which serves as a reference case in the whole set of copulas having the PQD property. Choices of appropriate distances and nonparametric estimators of copula are discussed, and the proposed methods are compared with testing procedures based on bootstrap and multiplier techniques. The consistency of the testing procedures is established. In a simulation study the authors investigate the finite sample size and power performances of three types of test statistics, Kolmogorov–Smirnov, Cramér–von‐Mises, and Anderson–Darling statistics, together with several nonparametric estimators of a copula, including recently developed kernel type estimators. Finally, they apply the testing procedures on some real data. The Canadian Journal of Statistics 38: 555–581; 2010 © 2010 Statistical Society of Canada     

A score test for monotonic trend in hazard rates for grouped survival data in stratified populations

Models for monotone trends in hazard rates for grouped survival data in stratified populations are introduced, and simple closed form score statistics for testing the significance of these trends are presented. The test statistics for some of the models understudy are shown to be independent of the assumed form of the function which relates the hazard rates to the sets of monotone scores assigned to the time intervals. The procedure is applied to test monotone trends in the recovery rates of erythematous response among skin cancer patients and controls that have been irradiated with a ultraviolent challenge.     

现行高校英语测试：问题与思考

目前我国有几种大型英语测试，如大学英语四、六级考试，英语专业四、八级考试，公共英语等级考试等，这些考试不可避免地存在一些共同的问题，即：考试制度不合理、信度和效度低、考试题型单一、阅卷评分有误差等。就上述问题提出了几点改革的设想。     

天然气电控发动机的开发研究

为满足天然气发动机数量将大幅度增长的需求,在某柴油机基础上通过改进燃烧系统和进气系统,设计高能点火系统、燃料供给系统、电控单元及传感器、执行器,并加装三元催化转换器,采用闭环空燃比控制等措施,研制了CNG（压缩天然气）单燃料电控多点顺序喷射发动机。实验结果表明天然气发动机的动力性能达到了设计指标,排放性能满足国家标准要求,设计方法切实可行。     

Test for cointegration based on two-stage least squares

A residual-based test for cointegration is proposed. The method of two-stage least squares is used to estimate the cointegration model parameters. The residuals are then tested for the existence of a unit root using the augmented Dickey-Fuller test.