Comparison of methods of estimation of parameters of the weibull distribution

The generalised least squares, maximum likelihood, Bain-Antle 1 and 2, and two mixed methods of estimating the parameters of the two-parameter Weibull distribution are compared. The comparison is made using (a) the observed relative efficiency of parameter estimates and (b) themean squared relative error in estimated quantiles, to summarize the results of 1000 simulated samples of sizes 10 and 25. The results are that: generalised least squares is the best method of estimating the shape parameter ß the best method of estimating the scale parameter a depends onthe size of ß for quantile estimation maximum likelihood is best Bain-Antle 2 is uniformly the worst of the methods.     

中国商业银行业实行分业经营的合理性分析

一、前言作为一种银行审慎经营管制手段 ,分业经营制度实质上是银行资产选择管制 ,隔离商业银行业务、投资银行业务与保险业务是其最主要的内容。除了资产选择管制 ,其它常用的审慎经营管制手段还有存款利率管制、资本充足性要求。世界各国都对银行业进行审慎经营管制的原因在于银行业不同于其他产业的特征 :首先 ,债务在银行资产结构中所占比重很大 ,且债权人极为分散 ;其次 ,除了可内部化的破产成本外 ,银行破产还存在高昂的社会成本。负债比重越大银行破产的概率越大 ,而债权人越分散债权人对银行资产运营监管能力和积极性越小。银行破产…     

Table of percentage points of ratios of linear combinations of order statistics of samples from exponential distributions

A form of the distribution function of ratios of linear combinations of order statistics of samples from an exponential distribution is given. From the distribution, tables of percentage points of the statistic for α = .05, .95, and n = 3(1)50, and for censoring up to five observations are presented. Use of the tables is made to find critical values of the most powerful scale and location invariant test of exponentiality against uniformity, and also to find critical values for a test of outliers in an exponential population.     

Minutes of Committee of Presidents of Statistical Societies

The general approach to generating random variates through transformations with multiple roots is discussed. Multinomial probabilities are determined for the selection of the different roots. An application of the general result yields a new and simple technique for the generation of variates from the inverse Gaussian distribution.     

Comparison of three estimators of the number of species

We consider estimation of the number of cells in a multinomial distribution. This is one version of the species problem: there are many applications, such as the estimation of the number of unobserved species of animals; estimation of vocabulary size, etc. We describe the results of a simulation comparison of three principal frequent-ist' procedures for estimating the number of cells (or species). The first procedure postulates a functional form for the cell probabilities; the second procedure approxi mates the distribution of the probabilities by a parametric probability density function; and the third procedure is based on an estimate of the sample coverage, i.e. the sum of the probabilities of the observed cells. Among the procedures studied, we find that the third (non-parametric) method is globally preferable; the second (functional parametric) method cannot be recommended; and that, when based on the inverse Gaussian density, the first method is competitive in some cases with the third method. We also discuss Sichel's recent generalized inverse Gaussian-based procedure which, with some refine ment, promises to perform at least as well as the non-parametric method in all cases.     

Comparison of dispersions of mixtures of ordered distributions

In the paper we consider mixtures of unknown stochastically ordered distribution functions according to known mixing distribution functions. We provide optimal lower and upper bounds on ratios of general dispersion measures of such mixtures. The bounds do not depend on the particular form of dispersion measure. We present applications of the results in reliability theory, insurance mathematics, Bayesian statistics, and regression analysis.     

论加强需求管理——对当前宏观经济形势的认识及其调控建议

１９９７年下半年开始,我国经济明显出现了居民消费需求不足,或者说,出现了供给相对过剩的发展态势。至１９９８年１２月已连续１５个月物价指数同比负增长,１９９８年商品零售价格下降２．６％,居民消费价格下降０．８％,可以认为这又是通货紧缩的重要征兆。出现需...     

中国国债融资功能的反思

一、中国国债融资制度的产生在传统计划经济体制下 ,中国的经济资源分配方式是 ,首先由国家强制集中全社会的资本要素 ,然后再用行政手段进行分配。从融资体制角度看 ,国家在这里充当了资本流动的中介 ,国家是融资的主体 ,它把资本从所有者那里筹集起来 ,再分配给他所选择的企业经营者使用 ,这种计划经济下的融资体制被称之为国家融资 (张春霖 ,2 0 0 0 )。在过去的几十年中 ,这种融资体制主要采取了两种基本形式 ,即收入融资和债务融资。所谓收入融资是指国家通过低工资、工农产品剪刀差等途径 ,把城乡居民应得的收入中可以用于长期储蓄的…     

A comparison of estimators of the precision of two instruments

Three different estimators of the variance in errors of measurement, or the “imprecisions” of instruments, have been proposed (Hahn and Nelson, 1970; Maxwell, 1974; Hanumara: 1975) for the case where two measurements by one instrument and one measurement by a second instrument are available for each item. The estimators are compared by studying the probabilities of negative values, the biases, the variances, and the mean square errors. Based on these results, Hahn and Nelson's estimators for the variances in errors of measurement are recommended. Simultaneous confidence intervals of the imprecisions of instruments are also given.     

Simulation of extremes of diffusions

The authors consider the problem of simulating the times of events such as extremes and barrier crossings in diffusion processes. They develop a rejection sampler based on Shepp [Shepp, Journal of Applied Probability 1979; 16:423–427] for simulating an extreme of a Brownian motion and use it in a general recursive scheme for more complex simulations, including simultaneous simulation of the minimum and maximum and application to more general diffusions. They price exotic options that are difficult to price analytically: a knock‐out barrier option with a modified payoff function, a lookback option that includes discounting at the risk‐free interest rate, and a chooser option where the choice is made at the time of a barrier crossing. The Canadian Journal of Statistics 38: 738–755; 2010 © 2010 Statistical Society of Canada