BARTLETT CORRECTED LIKELIHOOD RATIO TESTS IN LOCATION-SCALE NONLINEAR MODELS

The paper derives Bartlett corrections for improving the chisquare approximation to the likelihood ratio statistics in a class of location-scale family of distributions, which encompasses the elliptical family of distributions and also asymmetric distributions such as the extreme value distributions. We present, in matrix notation, a Bartlett corrected likelihood ratio statistic for testing that a subset of the nonlinear regression coefficients in this class of models equals a given vector of constants. The formulae derived are simple enough to be used analytically to obtain several Bartlett corrections in a variety of important models. We show that these formulae generalize a number of previously published results. We also present simulation results comparing the sizes and powers of the usual likelihood ratio tests and their Bartlett corrected versions when the scale parameter is considered known and when this parameter is uncorrectly specified.     

城市居民旅游环境影响与社会文化影响感知问卷量表的开发

城市居民旅游感知研究,对了解和掌握当地居民对旅游发展的态度与行为意义重大,是旅游地可持续发展的必然要求。作者针对国内城市居民旅游感知进行量表开发,先查阅了大量的国内外相关学术文献,接着进行了深入的文献研究,在此基础上设计了调查问卷初稿,问卷初稿包括居民旅游经济影响感知、旅游环境影响感知、旅游社会文化影响感知、旅游发展态度和满意的总体感知、居民参与旅游发展经营管理水平感知等五个维度,每个维度包括正面影响、负面影响两个构面。随后对初试问卷进行小样本调查,根据小样本调查的数据,使用统计分析软件SPSS16.0进行数据分析,对问卷量表进行信度和效度检验,对问卷测量题项进行净化,剔除相关度较低的测量项目,最终形成正式问卷。分析结果证明,量表具有很高的信度和效度。因篇幅所限,文章只对旅游环境影响感知、旅游社会文化影响感知二个维度的净化过程进行论述。     

A class of distribution-free tests for two-way layout

In this article a class of distribution-free tests for the hypothesis of no row (treatment) effect in a two-way layout design, with several observations per cell, is proposed. The tests are based on U-statistics, constructed by considering minima of all possible subsamples of same size from each cell.The proposed class of tests is compared with the parametric test, Mack and Skillings test and Yate's test for two-way layout, in terms of Pitman ARE sense. It is seen that for the case of equal number of observations per cell, the proposed tests have better efficiency for exponential and uniform error distributions.     

The power functions of the likelihood ratio tests for a simply ordered trend in normal means

Likelihood ratio tests for the homogeneity of k normal means with the alternative restricted by an increasing trend are considered as well as the likelihood ratio tests of the null hypothesis that the means satisfy the trend. While the work is primarily a survey of results concerning the power functions of these tests, the extensions of some results to the case of not necessarily equal sample sizes are presented. For the case of known or unknown population variances, exact expressions are given for the power functions for k=3,4, and approximations are discussed for larger k. The topics of consistency, bias and monotonicity of the power functions are included. Also, Bartholomew's conjectures concerning minimal and maximal powers are investigated, with results of a new numerical study given.     

Comparing Two Population Means and Variances: A Parametric Robust Way

Abstract

This article introduces a parametric robust way of comparing two population means and two population variances. With large samples the comparison of two means, under model misspecification, is lesser a problem, for, the validity of inference is protected by the central limit theorem. However, the assumption of normality is generally required, so that the inference for the ratio of two variances can be carried out by the familiar F statistic. A parametric robust approach that is insensitive to the distributional assumption will be proposed here. More specifically, it will be demonstrated that the normal likelihood function can be adjusted for asymptotically valid inferences for all underlying distributions with finite fourth moments. The normal likelihood function, on the other hand, is itself robust for the comparison of two means so that no adjustment is needed.     

“自上而下”阅读模式的实践及效果检验

在《日语阅读》课中导人“自上而下”阅读模式，着重对学生进行提高阅读的主动性，发挥已有知识在阅读过程中的作用，快速阅读文章，以及猜测生词读音，利用上下文推测词义等方面的训练。从对学生实施的问卷调查结果来看，教改对象对教改目的的认知程度较高，给予了普遍支持，对教学改革的效果也给予了高度评价。调查结果表明，在《日语阅读》课中导入“自上而下”阅读模式，可以有效提高学生的快速阅读能力，是切实可行的。     

A New Goodness-of-Fit Test Based on the Laplace Statistic for a Large Class of NHPP Models

ABSTRACT

Nonhomogeneous Poisson processes (NHPP) provide many models for hardware and software reliability analysis. In order to get an appropriate NHPP model, goodness-of-Fit (GOF for short) tests have to be carried out. For the power-law processes, lots of GOF tests have been developed. For other NHPP models, only the Conditional Probability Integral Transformation (CPIT) test has been proposed. However, the CPIT test is less powerful and cannot be applied to some NHPP models. This article proposes a general GOF test based on the Laplace statistic for a large class of NHPP models with intensity functions of the form αλ(t, β). The simulation results show that this test is more powerful than CPIT test.     

Testing non-oblique hypotheses

This paper considers a likelihood ratio test for testing hypotheses defined by non-oblique closed convex cones, satisfying the so called iteration projection property, in a set of k normal means. We obtain the critical values of the test using the Chi-Bar-Squared distribution. The obtuse cones are introduced as a particular class of cones which are non-oblique with every one of their faces. Examples with the simple tree order cone and the total order cone are given to illustrate the results.     

Inferences on the lognormal mean for complete samples

In many engineering problems it is necessary to draw statistical inferences on the mean of a lognormal distribution based on a complete sample of observations. Statistical demonstration of mean time to repair (MTTR) is one example. Although optimum confidence intervals and hypothesis tests for the lognormal mean have been developed, they are difficult to use, requiring extensive tables and/or a computer. In this paper, simplified conservative methods for calculating confidence intervals or hypothesis tests for the lognormal mean are presented. In this paper, “conservative” refers to confidence intervals (hypothesis tests) whose infimum coverage probability (supremum probability of rejecting the null hypothesis taken over parameter values under the null hypothesis) equals the nominal level. The term “conservative” has obvious implications to confidence intervals (they are “wider” in some sense than their optimum or exact counterparts). Applying the term “conservative” to hypothesis tests should not be confusing if it is remembered that this implies that their equivalent confidence intervals are conservative. No implication of optimality is intended for these conservative procedures. It is emphasized that these are direct statistical inference methods for the lognormal mean, as opposed to the already well-known methods for the parameters of the underlying normal distribution. The method currently employed in MIL-STD-471A for statistical demonstration of MTTR is analyzed and compared to the new method in terms of asymptotic relative efficiency. The new methods are also compared to the optimum methods derived by Land (1971, 1973).     

SoC软硬件协同技术的FPGA芯片测试新方法

针对传统的基于纯硬件平台的FPGA芯片测试方法所存在的种种问题,提出并验证了一种基于软硬件协同技术的FPGA芯片测试方法。该方法引入了软件的灵活性与可观测性等软件技术优势,具有存储深度大、可测I/O管脚数目多、自动完成配置下载(不需人工干预)和自动定位FPGA中的错误等优点,提高了FPGA的测试速度和可靠性,并降低了测试成本,与传统的自动测试仪(ATE)相比有较高的性价比。采用软硬件协同方式针对Xilinx4010的I/O单元进行了测试,实现了对FPGA芯片的自动反复配置、测试和错误定位。