关于英语口语能力测试信度的思考

测试信度是与效度同等重要的考试学理论。口试作为一种主观性考试 ,其信度评估一直制约口试的推广。本文运用美国语言学家奥勒 (JohnW .Oller;Jr)的“语用期待语法规则”理论 ,把口试作为一种交际性测试来研究 ,结合口试实践 ,分析影响口试信度的因素 ,以及提高口试信度的方式。     

Statistical inference for start-up demonstration tests with rejection of units upon observing d failures

In this paper, we consider the statistical inference for the success probability in the case of start-up demonstration tests in which rejection of units is possible when a pre-fixed number of failures is observed before the required number of consecutive successes are achieved for acceptance of the unit. Since the expected value of the stopping time is not a monotone function of the unknown parameter, the method of moments is not useful in this situation. Therefore, we discuss two estimation methods for the success probability: (1) the maximum likelihood estimation (MLE) via the expectation-maximization (EM) algorithm and (2) Bayesian estimation with a beta prior. We examine the small-sample properties of the MLE and Bayesian estimator. Finally, we present an example to illustrate the method of inference discussed here.     

On some pre-test and Stein-rule phi-divergence test estimators in the independence model of categorical data

For the model of independence in a two way contingency table, shrinkage estimators based on minimum φ$\phi$-divergence estimators and φ$\phi$-divergence statistics are considered. These estimators are based on the James–Stein-type rule and incorporate the idea of preliminary test estimator. The asymptotic bias and risk are obtained under contiguous alternative hypotheses, and on the basis of them a comparison study is carried out.     

On the joint distribution of placement statistics under progressive censoring and applications to precedence test

In reliability and survival analysis, comparison of two or more populations is an important problem. For example, while comparing a treatment group with a control group, one may be interested in determining whether the observations in the treatment group have a longer lifetime than those from the control group, that is, whether the treatment is effective or not. In such a study, it would be extremely valuable to make a decision based on early failures. In this paper, we consider independent progressively Type-II censored random samples from two populations with cumulative distribution function's (cdf) F(·)$F(·)$ and G(·)$G(·)$ respectively, and discuss a precedence test for testing the equality of the two distributions based on placements. For this purpose, we derive the joint distribution of the first l   placement statistics from the progressively censored sample from F(·)$F(·)$. We then derive the exact null distribution of the precedence test statistic which is simply the sum of the placements. We provide the rejection regions for fixed levels of significance and various sample sizes and different progressive censoring schemes.     

基于平均自下而上时间的两种分类方法的比较

内容提要：诸如疾病分类系统的预后预测和分类方法,常可用于帮助进行临床管理决策。同一疾病总体常可得到多种分类方法,因此有必要比较这些方法以确定最优分类,或者寻找不逊于最优分类的替代方法。本文基于约束平均寿命引入分离度指标来度量分类方法的预后分类效率,这个指标可用来比较以生存时间为结局的两种分类方法的功效,特别是用于非劣性和等效性检验。我们给出了基于配对数据的两个分离度的估计与检验方法。模拟结果提示,检验方法在适当的样本量条件下能够控制第一类错误,两个实例表明在医学临床中的应用。     

我国货币市场的非均衡性检验

识别和检验货币市场的非均衡性是重要的,尤其是透过货币乘数、货币流通速度识别和检验货币市场运行态势。检验的结果支持我国货币市场存在需求高于供给的非均衡判断。同时,由于近年来货币增长率一直高于产出增长率,GDP与货币量的比值偏低,市场的货币沉积现象比较严重,在一定程度上存在通货膨胀隐患。因此,货币供给的控制不宜适应需求,应当从降低货币沉积和增强流动性上缓解货币供求的非均衡问题。     

How robust are tests for two independent samples?

Non-parametric procedures are sometimes in use even in cases where the corresponding parametric procedure is preferable. This is mainly due to the fact that in practical applications of statistical methods too much attention is paid to any violation of the normality assumption–normal distribution is, however, primarily supposed in order to easily derive the exact distribution of the statistic used within parametric approaches.     

Generalized inferences on the common mean vector of several multivariate normal populations

The hypothesis testing and confidence region are considered for the common mean vector of several multivariate normal populations when the covariance matrices are unknown and possibly unequal. A generalized confidence region is derived using the concepts of generalized method based on the generalized p$p$-value. The generalized confidence region is illustrated with two numerical examples. The merits of the proposed method are numerically compared with those of existing methods with respect to their expected area or expected d-dimensional volumes and coverage probabilities under different scenarios.     

Inferences on correlation coefficients: One-sample,independent and correlated cases

This article concerns inference on the correlation coefficients of a multivariate normal distribution. Inferential procedures based on the concepts of generalized variables (GVs) and generalized p$p$-values are proposed for elements of a correlation matrix. For the simple correlation coefficient, the merits of the generalized confidence limits and other approximate methods are evaluated using a numerical study. The study indicates that the proposed generalized confidence limits are uniformly most accurate even for samples as small as three. The results are extended for comparing two independent correlations, overlapping and non-overlapping dependent correlations. For each problem, the properties of the GV approach and other asymptotic methods are evaluated using Monte Carlo simulation. The GV approach produces satisfactory results for all the problems considered. The methods are illustrated using a few practical examples.     

Maximum log-likelihood ratio test for a change in three parameter Weibull distribution

Asymptotic behavior of a log-likelihood ratio statistic for testing a change in a three parameter Weibull distribution is studied. It is shown that if a shape parameter α>2$\alpha >2$ the law of iterated logarithm for maximum-likelihood estimators is still valid and the log-likelihood testing statistic is asymptotically distributed (after an appropriate normalization) according to a Gumbel distribution.