Characteristic properties of multivariate survival functions in terms of residual life distributions

This paper discusses the relationships among some characteristic properties of the multivariate survival function based on the residual life distribution, and provides the conditions for their equivalence. In the meanwhile, the corrected version of Ma (1996, Theorem 1 (ii) and (iii)) is given.     

Percentage Points of the Multivariate t Distribution

The known methods for computing percentage points of multivariate t distributions are reviewed. We believe that this review will serve as an important reference and encourage further research activities in the area.     

Multivariate survival functions characterized by constant product of mean remaining lives and hazard rates

Under the assumption that the products of multivariate mean remaining lives and hazard rates are the same constant, it is shown that the corresponding multivariate survival function belongs to one of three families: (1) multivariate Gumbel exponential distribution; (2) multivariate Lomax (Pareto type II) distribution; (3) multivariate rescaled Dirichlet distribution. This result is then used to derive another characterization of the latter two families based on the residual life distribution.     

Selection of the best population: an information theoretic approach

This paper is devoted to the statistical problem of ranking and selection populations by using the subset selection formulation. The interest is focused (i) on the selection of the best population among k independent populations and (ii) on the selection of the best population, which is closest to an additional standard or control population. With respect to the first problem the populations are ranked in terms of entropies of their distributions and the population whose distribution has maximum entropy is selected. For the second problem the populations are ranked in terms of divergences between their distributions and the distribution of the standard or control population and the population with the minimum divergence is selected. In each case the populations are assumed to have general parametric densities satisfying the classical regularity conditions of asymptotic statistic. Large sample properties of the estimators of entropies and divergences of the populations will be studied and used in order to determine the probabilities of correct selection of the proposed asymptotic selection rules. Illustrative examples, including a numerical example using real medical data appeared in the literature, will be given for multivariate homoscedastic normal populations and populations described by the regular exponential family of distributions. Received December 2001     

On the standarized empirical process

In this note a new proof of a theorem of CSAKI (1975, 1982) concerning the almost sure behaviour of the standardized empirical process is established.     

PERFORMANCE OF MURPHY'S TEST FOR TWO OUTLIERS IN A LINEAR MODEL

Abstract. In JOSHI and LALITHA (1986) a test for two outliers in the same direction in a linear model is discussed. Here the performance of this statistic is studied. For this, the exact non–null density function of the random variables involved in defining the statistic is obtained. Then a measure of performance is defined and it is applied to the case of a random sample from a normal distribution, as in this case the above said statistic reduces to the well known Murphy's test statistic. These values are then compared with the power values obtained by HAWKINS (1978).     

Moment inequalities for order statistics with applications to characterizations of distributions

General inequalities of Hölder type between moments of order statistics and moments of record values respectively are derived. Special choices of the involved sample sizes and ranks and discussions of when equality is attained in these inequalities yield several characterizations of well known distributions, such as the uniform, polynomial, Pareto, reflected Pareto, exponential, Weibull distribution and some others.     

Approximation for the cumulative and inverse gamma distribution

The gamma distribution function can be expressed in terms of the Normal distribution and density functions with sufficient accuracy for most practical purposes.
The distribution function for the density x^Λ-1e^-x/μ/μ^ΛΓ(A) on 0 -R(Λ){(1 + 1/1 2Λ) φ(z) + 11 -z/4Λ^1/2+2(z²+ 2)/45Λ] φ(z) /3 Λ^1/2} where φ(z)≅1/[1 +_e^{-2z(√2/π+z2 /28)}] and φ(z) = e^{-z2 /2}/√2π are the Normal distribution and density functions, y is the appropriate root of y-y²/6+y³/36-y⁴/270= In (x/Λμ), z= Λ^1/2 y, and R( Λ) is the remainder term in Stirling's approximation for In Γ(Λ).     

On rankings and top choices in random utility models with dependent utilities

Different aggregate preference orders based on rankings and top choices have been defined in the literature to describe preferences among items in a fixed set of alternatives. A useful tool in this framework is constituted by random utility models, where the utility of each alternative, or object, is represented by a random variable, indexed by the object, which, for example, can capture the variability of preferences over a population. Applications are derived in diverse research fields, including computer science, management science and reliability. Recently, some stochastic ordering conditions have been provided for comparing alternatives by means of some aggregate preference orders in the case of independent random utility variables by Joe (Math Soc Sci 43:391–404, 2002). In this paper we provide new conditions, based on some joint stochastic orderings, for aggregate preference orders among the alternatives in the case of dependent random utilities. We also provide some examples of application in different research fields.      

浅析咸阳市纺织企业联建销售共同配送中心的必要性

作为咸阳的支柱产业——纺织业,经过市场竞争,由于销售渠道不通畅等原因,造成咸阳纺织业萎缩。要重塑咸阳纺织业的活力,需在我市联建纺织销售共同配送中心,以提高其市场竞争力。本文在分析咸阳纺织现状基础之上,对咸阳市纺织业联建销售共同配送中心相关问题进行了初步研究分析。针对要解决的问题,分析联建销售共同配送中心的必要性及可行性。     

PERFORMANCE OF STUDENTIZED RANGE STATISTIC FOR TWO OUTLIERS IN A LINEAR MODEL

Abstract. In JOSHI and LALITHA (1986) a statistic K is proposed for detecting two outliers present in the opposite directions in a linear model. This statistic reduces to the Studentized range statistic for the case of a simple random sample from a normal population. In this paper, the performance of this statistic is studied. For this an approximate non–null density of the random variables involved in defining the statistic is derived. An exact density is also obtained by using the methods of LALITHA and JOSHI (1986), where the results are proved for Murphy's statistic. A measure of performance is then defined and an example is also given for highlighting the usage of the above said statistic.     

The distribution function of a statistic for testing the equality of scale parameters in two gamma populations

Summary The exact distribution function of the ratio of two sums of gamma variates is derived in this paper. The result applies to ratios of quadratic forms and to a statistic used for testing the equality of scale parameters in two gamma populations.     

代理配送业务订单处理相关问题研究

针对第三方物流企业的代理配送业务，通过将客户订单内容转化为对企业特定时间内配送能力的占用需求，提出了一个整数规划模型，并给出了求解方法和一个计算实例。     

On the independence of integer and fractional parts

We use the independence of the integer and fractional parts of exponentially distributed random variables to obtain expressions for the order statistics from a geometric distribution. As our main result we show that a strong form of this independence characterizes the exponential distribution.     

On the structure and estimation of hierarchical Archimedean copulas

In this paper we provide a method for estimating multivariate distributions defined through hierarchical Archimedean copulas. In general, the true structure of the hierarchy is unknown, but we develop a computationally efficient technique to determine it from the data. For this purpose we introduce a hierarchical estimation procedure for the parameters and provide an asymptotic analysis. We consider both parametric and nonparametric estimation of the marginal distributions. A simulation study and an empirical application show the effectiveness of the grouping procedure in the sense of structure selection.