Proper Bayes minimax estimators of the normal mean matrix with common unknown variances

This paper addresses the problem of estimating a matrix of the normal means, where the variances are unknown but common. The approach to this problem is provided by a hierarchical Bayes modeling for which the first stage prior for the means is matrix-variate normal distribution with mean zero matrix and a covariance structure and the second stage prior for the covariance is similar to Jeffreys’ rule. The resulting hierarchical Bayes estimators relative to the quadratic loss function belong to a class of matricial shrinkage estimators. Certain conditions are obtained for admissibility and minimaxity of the hierarchical Bayes estimators.     

管理层持股、领导权结构与财务重述

本文以我国2005-2009年间A股市场补充与更正报告中出现"会计差错更正"项目的公司为研究对象,以是否发生财务重述为因变量,采用配对样本分析的Logit回归方法研究了管理层持股、领导权结构与财务重述之间的关系。本研究发现,管理层持股比例与财务重述之间存在显著的U型关系,领导权结构对财务重述没有显著影响,然而管理层持股的利益协同效应(堑壕效应)在两职分离(两职合一)的公司中更容易得到发挥。本研究发展了财务重述、管理层持股以及领导权结构的研究内容,为完善公司治理机制、防范会计错报提供了相应的思路。     

建立最优回归方程的一种新方法

本文提出了一种新的建立最优回归方程的方法,即t统计量法。应用实践表明该方法完全能够建立起最优回归方程。     

An access network design problem with end-to-end QoS constraints

In this paper, we present an access network design problem with end-to-end quality of service (QoS) requirement. The problem can be conceptualized as a two-level hierarchical location-allocation problem on the tree topology with nonlinear side constraints. The objective function of the nonlinear mixed integer programming model minimizes the total cost of switch and fiber cable, while satisfying demand within the prescribed level of QoS. By exploiting the inherent structure of the nonlinear QoS constraints, we develop linearization techniques for finding an optimal solution. Also, we devise an effective exact optimal algorithm within the context of disjunctive constraint generation. We present promising computational results that demonstrate the effectiveness of the proposed solution procedure.     

改进灰色预测在油田多目标规划决策中的应用

建立了S油田勘探、开发、炼化、机械、公用工程等多个部门和全局的非线性多级目标优化规划模型,应用关联分析、改进灰色预测、回归分析求取规划模型的约束方程并线性化;编制了相应的计算软件,使之快速预测和优化油田各部门“九五”各年的投资和产值;并将优化结果与油田过去或计划值加以对比,给油田规划决策带来一定的参考。     

A Bayesian model for ranking hazardous road sites

Summary.  Road safety has recently become a major concern in most modern societies. The identification of sites that are more dangerous than others (black spots) can help in better scheduling road safety policies. This paper proposes a methodology for ranking sites according to their level of hazard. The model is innovative in at least two respects. Firstly, it makes use of all relevant information per accident location, including the total number of accidents and the number of fatalities, as well as the number of slight and serious injuries. Secondly, the model includes the use of a cost function to rank the sites with respect to their total expected cost to society. Bayesian estimation for the model via a Markov chain Monte Carlo approach is proposed. Accident data from 519 intersections in Leuven (Belgium) are used to illustrate the methodology proposed. Furthermore, different cost functions are used to show the effect of the proposed method on the use of different costs per type of injury.     

改革开放后北京、上海、广州对流动人口的经济拉力因素的分析

本文以推拉理论建立多元线性模型并运用逐步回归的方法,分析改革开放后北京、上海、广州吸引流动人口流入的经济因素。结果显示流动人口主要依据微观经济因素做出流动迁移决策;不同城市对流动人口产生拉力的具体的微观经济因素不尽相同,即使有相同经济拉力因素的城市,拉力的大小也有差异;三城市的流动人口就业的分布不同,广州流动人口就业集中分布于第三产业,北京和上海则不然。     

More Efficient Tests Robust to Heteroskedasticity of Unknown Form

In the presence of heteroskedasticity of unknown form, the Ordinary Least Squares parameter estimator becomes inefficient, and its covariance matrix estimator inconsistent. Eicker (1963) and White (1980) were the first to propose a robust consistent covariance matrix estimator, that permits asymptotically correct inference. This estimator is widely used in practice. Cragg (1983) proposed a more efficient estimator, but concluded that tests basd on it are unreliable. Thus, this last estimator has not been used in practice. This article is concerned with finite sample properties of tests robust to heteroskedasticity of unknown form. Our results suggest that reliable and more efficient tests can be obtained with the Cragg estimators in small samples.     

The ubiquitous angle

Summary.  Previously we used the geometry of n -dimensional space to derive the paired samples t -test and its p -value. In the present paper we describe the 'ubiquitous' application of these results to single degree of freedom linear model hypothesis tests. As examples, we derive the p - and t -values for the independent samples t -test, for testing a contrast in an analysis of variance and for testing the slope in a simple linear regression analysis. An angle θ in n -dimensional space is again pivotal in the development of the ideas. The relationships between p , t , θ , F and the correlation coefficient are also described by using a 'statistical triangle'.