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21.
A general method for determining Pitman Nearness is given In the case of univariate estimators. This method is then applied to some estimation problems. The concept of Pitman Nearness is also generalized to the multivariate case. The James-Stein estimators are used to illustrate the multivariate comparison.  相似文献   
22.
This paper derives a test statistic for the variance-covariance parameters which is a quadratic function of their MINQUE (Minimum Norm Quadratic Unbiased Estimation) estimates. The test is a Wald-type test, and its development closely parallels the theory used to derive a similar test for the coefficients in linear models. In fact, the derivation proceeds by first setting up the estimation problem in a derived linear model in which the dispersion parameters are the coefficients. The test statistic is shown to be the sum of the squares of independent standardized x2 variables.  相似文献   
23.
This paper surveys recent developments in the strong law of large numbers for dependent heterogeneous processes. We prove a generalised version of a recent strong law for Lz-mixingales, and also a new strong law for Lpmixingales. These results greatly relax the dependence and heterogeneity conditions relative to those currently cited, and introduce explicit trade-offs between dependence and heterogeneity. The results are applied to proving strong laws for near-epoch dependent functions of mixing processes. We contrast several methods for obtaining these results, including mapping directly to the mixingale properties, and applying a truncation argument.  相似文献   
24.
This article addresses the problem of testing the null hypothesis H0 that a random sample of size n is from a distribution with the completely specified continuous cumulative distribution function Fn(x). Kolmogorov-type tests for H0 are based on the statistics C+ n = Sup[Fn(x)?F0(x)] and C? n=Sup[F0(x)?Fn(x)], where Fn(x) is an empirical distribution function. Let F(x) be the true cumulative distribution function, and consider the ordered alternative H1: F(x)≥F0(x) for all x and with strict inequality for some x. Although it is natural to reject H0 and accept H1 if C + n is large, this article shows that a test that is superior in some ways rejects F0 and accepts H1 if Cmdash n is small. Properties of the two tests are compared based on theoretical results and simulated results.  相似文献   
25.
Cross-classified data are often obtained in controlled experimental situations and in epidemiologic studies. As an example of the latter, occupational health studies sometimes require personal exposure measurements on a random sample of workers from one or more job groups, in one or more plant locations, on several different sampling dates. Because the marginal distributions of exposure data from such studies are generally right-skewed and well-approximated as lognormal, researchers in this area often consider the use of ANOVA models after a logarithmic transformation. While it is then of interest to estimate original-scale population parameters (e.g., the overall mean and variance), standard candidates such as maximum likelihood estimators (MLEs) can be unstable and highly biased. Uniformly minimum variance unbiased (UMVU) cstiniators offer a viable alternative, and are adaptable to sampling schemes that are typiral of experimental or epidemiologic studies. In this paper, we provide UMVU estimators for the mean and variance under two random effects ANOVA models for logtransformed data. We illustrate substantial mean squared error gains relative to the MLE when estimating the mean under a one-way classification. We illustrate that the results can readily be extended to encompass a useful class of purely random effects models, provided that the study data are balanced.  相似文献   
26.
Results from classical linear regression regarding the effects of covariate adjustment, with respect to the issues of confounding, the precision with which an exposure effect can be estimated, and the efficiency of hypothesis tests for no treatment effect in randomized experiments, are often assumed to apply more generally to other types of regression models. In this paper results pertaining to several generalized linear models involving a dichotomous response variable are given, demonstrating that with respect to the issues of confounding and precision, for models having a linear or log link function the results of classical linear regression do generally apply, whereas for other models, including those having a logit, probit, log-log, complementary log-log, or generalized logistic link function, the results of classical linear regression do not always apply. It is also shown, however, that for any link function, covariate adjustment results in improved efficiency of hypothesis tests for no treatment effect in randomized experiments, and hence that the classical linear regression results regarding efficiency do apply for all models having a dichotomous response variable.  相似文献   
27.
A measure of multivariate correlation between two sets of vectors is considered when the underlying joint distribution is a member of the class of elliptical distributions. Its asymptotic distribution is derived under different situations and these results are used to test hypotheses on vector correlation when the underlying joint distribution is non-normal.  相似文献   
28.
Summary.  We propose covariance-regularized regression, a family of methods for prediction in high dimensional settings that uses a shrunken estimate of the inverse covariance matrix of the features to achieve superior prediction. An estimate of the inverse covariance matrix is obtained by maximizing the log-likelihood of the data, under a multivariate normal model, subject to a penalty; it is then used to estimate coefficients for the regression of the response onto the features. We show that ridge regression, the lasso and the elastic net are special cases of covariance-regularized regression, and we demonstrate that certain previously unexplored forms of covariance-regularized regression can outperform existing methods in a range of situations. The covariance-regularized regression framework is extended to generalized linear models and linear discriminant analysis, and is used to analyse gene expression data sets with multiple class and survival outcomes.  相似文献   
29.
This installment of "Serials Spoken Here" covers events that transpired between late September and late October 2008. Reported herein are two Webinars, one on ONIX for Serials, the other on SUSHI, and two conferences: the eighty-fourth annual Meeting of the Potomac Technical Processing Librarians and the New England Library Association's Annual Conference.  相似文献   
30.
对内蒙古东部、安第斯山北部和美洲中部三个地区的早期酋长制群体的聚落形态进 行的比较研究表明,尽管这三个地区的发展过程大致相当,但在这三个地区中,大体类似的转变 却以不同的方式发生,从而导致了三个各具特色的等级社会的出现。最初的、大规模的、以等级 制度原则组织起来的酋长制群体出现后,其发展轨道的早期阶段明显地为后来的、较大的、更复 杂的政治实体即国家的出现创造了条件。通过地域性聚落分析,可以发现这三个地区在不同规模 层次上的人口和社会组织的异同,其中在赤峰和奥哈卡(Oaxaca)地区都存在的小型群体却不见 于马格达雷那高地(AltoMagdalena)的现象,需要进行更深入的研究,才能进一步揭示出在马 格达雷那高地是什么样的社会交流把这些家庭联合成更大的社会团体。  相似文献   
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