Assessing and Improving the Performance of Nearly Efficient Unit Root Tests in Small Samples

Abstract

The development of unit root tests continues unabated, with many recent contributions using techniques such as generalized least squares (GLS) detrending and recursive detrending to improve the power of the test. In this article, the relation between the seemingly disparate tests is demonstrated by algebraically nesting all of them as ratios of quadratic forms in normal variables. By doing so, and using the exact sampling distribution of the ratio, it is straightforward to compute, examine, and compare the test' critical values and power functions. It is shown that use of GLS detrending parameters other than those recommended in the literature can lead to substantial power improvements. The open and important question regarding the nature of the first observation is addressed. Tests with high power are proposed irrespective of the distribution of the initial observation, which should be of great use in practical applications.     

Dividend barrier and ruin problems for a risk model with delayed claims

In this paper, a compound Poisson risk model in the presence of a constant dividend barrier is considered. Two types of individual claims, main claims and by-claims, are defined, where every by-claim is induced by the main claim and and the time of delay for the claim is assumed to be random. A system of integro-differential equations with certain boundary conditions for the expected discounted penalty function is derived. We show that its solution can be expressed as the solution to the expected discounted penalty function in the same risk model with the absence of a barrier plus a linear combination of two linearly independent solutions to the associated homogeneous integro-differential equation. Using systems of integro-differential equations for the moment-generating function as well as for the arbitrary moments of the sum of discounted dividend payments until ruin, a matrix version of the dividends–penalty type relationship is derived. We also prove that ruin is certain under constant dividend barrier strategy. The closed form expressions are given when the claim amounts from both classes are exponentially distributed. Finally, a numerical example is presented to illustrate the solution procedure.     

Minimax property of stein's estimator

Stein's estimator and some other estimators of the mean of a K-variate normal distribution are known to dominate the maximum likelihood estimator under quadratic loss for K > 3, and are therefore minimax. In this paper it is shown that the minimax property of Stein's rule is preserved with respect to a generalized loss function.     

On shrinkage m-estimators of location parameters

For a general class of continuous ( and marginally symmetric ) inultivariate distributions, based on suitable M-statistics ( involving bounded but possibly discontinuous score generating functions), shrinkage estimators of location are considered. These estimators are based on the James-Stein type rule and incorporates the idea of preliminary test estimation too. The main emphasis is laid on the study of asymptotic tdistributional ) risk properties of these est-innators, and asymptotic tin-) adraissibility results are also studied under fairly general regularity conditions.     

Estimation of signal to noise ratio using mahalanobis distance

In this paper, we propose some alternative estimatiors to that given by C. G. Khatri and C. R. Rao (1985), for estimating Signal to Noise ratio. Using Pitman Nearness, Condition for prefering one estimator over the other is estabilished. It is shown numerically that estimators corresponding to Entropy loss function are better more oftern than those corresponding to Squared Error loss.     

On Comparison Of Estimates Of Dispersion Using Generalized Pitman Nearness Criterion

In this paper, estimates QP dispersion matrix and its functions are compared based on generalized Pitman nearness criterion, Various Iosa functions are considered for the purpose. Locally superior estimates are defined and obtained. Comparison of these estimates are made with other standard ones. It is snown that within certain classes, defined in the paper, these are the best estimatcrs ia the generalized Fitman nearness sense     

基于不确定因素的食品安全问题频发的伦理分析

不良食品生产行为给社会带来的危害应由食品生产者及相关的政府职能部门负担起相应的伦理及法律责任。政府职能部门责任伦理意识缺失、消费者生命健康意识淡薄及社会道德监督机制缺失,造成了政府监管、公众安全认知、食品生产行业的道德与法律风险等方面的不确定性,成为食品安全事故频发的深层根源。只有通过健全食品安全监管制度、建构政府信用问责机制,提高政府监管者的责任伦理素养,培养公众的生命健康意识和食品安全问题防范意识,建立食品供应链道德信用跟踪系统,才能真正解决食品安全问题。     

Analysis of all-zero binomial outcomes with borderline and equilibrium priors

This article is concerned with the analysis of a random sample from a binomial distribution when all the outcomes are zero (or unity). We discuss how elicitation of the prior can be reduced to asking the expert whether (and which of) the so-called borderline or equilibrium priors are plausible.     

基于经济伦理的腐败问题研究

经济伦理一直是学术界所关注的重要问题,尤其是由经济伦理缺失所导致的腐败问题日益受到关注。文章从经济伦理角度出发,通过构建经济伦理的决策模型,对腐败行为的产生和腐败问题的治理做出分析。文章指出,腐败行为的产生是行政人员根据期望收益的决策过程,其核心内容是经济性和伦理性的内在博弈。对于腐败的治理,要从制度调整、监控体系以及伦理规范三个方面做出,以提高腐败行为的成本,降低腐败的期望收益,从根本上抑制腐败行为的发生。     

企业科技人才雇佣关系内容维度的实证研究

不同样本的探索性因子分析和验证性因子分析表明,企业对科技人才提供的回报和期望的 贡献都是多维度的概念。企业对科技人才提供的回报有三个维度,即尊重科技人才、个人成长和物质回 报 ;企业对科技人才期望的贡献也有三个维度,即专业素质、认同组织和奉献精神。这些维度与以往文献 中针对其他员工群体的研究结果既有相似性,也有独特性。进一步分析发现,虽然绝大多数样本企业采 用平衡的雇佣关系模式,即工作导向型和组织导向型,但也分别有1/8左右的样本企业采用两种不平衡 的雇佣关系模式,即投入过度型和投入不足型。