Call my bluff

Poker used to be the card game of choice for hard men late at night in smoke-filled rooms. Now online poker is bidding for respectability and a site on the home computer. Phil Woodward gives us the straight dope.     

呼唤国家信用体系的建立

诚信为本、有容乃大建立国家信用体系乃当务之急信用可以是一个广义的定义,也可以范围很窄,广义的信用是二元主体或多元主体之间,以某种经济生活需要为目的,建立在诚实守信基础上的心理承诺与约期实践相结合的意志和能力; 狭义的信用是以授信人（债权人）对于受信人（债务人）所作还款承诺和能力有没有信心为基础,决定是否同意产生授信人到受信人的经济价值转移,其中定义有明确的时间因素。本文所讨论的主要是狭义的信用。要保证经济生活中的血脉—金融能够流通顺畅,就必须拥有有效的支付手段。在经济领域,支付手段除了现金以外,另…     

Lower bounds for confidence coefficients for confidence intervals for finite population quantiles

Assuming stratified simple random sampling, a confidence interval for a finite population quantile may be desired. Using a confidence interval with endpoints given by order statistics from the combined stratified sample, several procedures to obtain lower bounds (and approximations for the lower bounds) for the confidence coefficients are presented. The procedures differ with respect to the amount of prior information assumed about the var-iate values in the finite population, and the extent to which sample data is used to estimate the lower bounds.     

Multilevel models for longitudinal variables prognostic for survival

The issue of modelling the joint distribution of survival time and of prognostic variables measured periodically has recently become of interest in the AIDS literature but is of relevance in other applications. The focus of this paper is on clinical trials where follow-up measurements of potentially prognostic variables are often collected but not routinely used. These measurements can be used to study the biological evolution of the disease of interest; in particular the effect of an active treatment can be examined by comparing the time profiles of patients in the active and placebo group. It is proposed to use multilevel regression analysis to model the individual repeated observations as function of time and, possibly, treatment. To address the problem of informative drop-out—which may arise if deaths (or any other censoring events) are related to the unobserved values of the prognostic variables—we analyse sequentially overlapping portions of the follow-up information. An example arising from a randomized clinical trial for the treatment of primary biliary cirrhosis is examined in detail.     

Correctings tests for trend in proportions for skewness

We develop the score test for the hypothesis that a parameter of a Markov sequence is constant over time, against the alternatives that it varies over time, i.e., θ_t = θ + U_t; t = 1,2,…, where {U_t; t = 1,2,...} is a sequence of independently and identically distributed random variables with mean zero and variance σ^z _u and θ is a fixed constant. The asymptotic null distribution of the test statistic is proved to be normal. We illustrate our procedure by examples and a real life data analysis.     

Graphical technique for comparing designs for random models

Methods for comparing designs for a random (or mixed) linear model have focused primarily on criteria based on single-valued functions. In general, these functions are difficult to use, because of their complex forms, in addition to their dependence on the model's unknown variance components. In this paper, a graphical approach is presented for comparing designs for random models. The one-way model is used for illustration. The proposed approach is based on using quantiles of an estimator of a function of the variance components. The dependence of these quantiles on the true values of the variance components is depicted by plotting the so-called quantile dispersion graphs (QDGs), which provide a comprehensive picture of the quality of estimation obtained with a given design. The QDGs can therefore be used to compare several candidate designs. Two methods of estimation of variance components are considered, namely analysis of variance and maximum-likelihood estimation.     

Inference for domains under imputation for missing survey data

The authors study the estimation of domain totals and means under survey‐weighted regression imputation for missing items. They use two different approaches to inference: (i) design‐based with uniform response within classes; (ii) model‐assisted with ignorable response and an imputation model. They show that the imputed domain estimators are biased under (i) but approximately unbiased under (ii). They obtain a bias‐adjusted estimator that is approximately unbiased under (i) or (ii). They also derive linearization variance estimators. They report the results of a simulation study on the bias ratio and efficiency of alternative estimators, including a complete case estimator that requires the knowledge of response indicators.     

Small sample distribution for a nonparametric test for trend

The exact distribution of a nonparametric test statistic for ordered alternatives, the _rank ² statistic, is computed for small sample sizes. The exact distribution is compared to an approximation.     

Truncation bounds for infinite expansions for the stable distributions

A number of authors have presented tabulations for the stable distributions based on infinite expansions for the density functions. In this paper we derive exact bounds for the truncation errors in these expansions and use the results to comment on some of the problems that have arisen in tabulating the stable distribution functions. The derivation of the truncation bounds relies on a little-known result for complex argument Taylor series due to Darboux (1876) which IS of much wider applicability than the present context.     

Markov Chain Monte Carlo for Exact Inference for Diffusions

ABSTRACT. We develop exact Markov chain Monte Carlo methods for discretely sampled, directly and indirectly observed diffusions. The qualification ‘exact’ refers to the fact that the invariant and limiting distribution of the Markov chains is the posterior distribution of the parameters free of any discretization error. The class of processes to which our methods directly apply are those which can be simulated using the most general to date exact simulation algorithm. The article introduces various methods to boost the performance of the basic scheme, including reparametrizations and auxiliary Poisson sampling. We contrast both theoretically and empirically how this new approach compares to irreducible high frequency imputation, which is the state‐of‐the‐art alternative for the class of processes we consider, and we uncover intriguing connections. All methods discussed in the article are tested on typical examples.     

Inequalities for tail probabilities for the multivariate normal distribution

Inequalities for tail probabilities of the multivariate normal distribution are obtained, as a generalization of those given by Feller (1966). Upper and lower bounds are given in the equi-correlated case. For an arbitrary correlation matrix R, an upper bound is obtained, using a result of Slepian (1962) which asserts that certain multivariate normal probabilities are a non-decreasing function of correlations.     

Methods for diagnosing multiplicative-interaction models for two-way contingency tables

An expanded class of multiplicative-interaction (M-I) models is proposed for two-way contingency tables. These models a generalization of Goodman's association models, fill in the gap between the independence and the saturated models. Diagnostic rules based on a transformation of the data are proposed for the detection of such models. These rules, utilizing the singular value decomposition of the transformed data, are very easy to use. Maximum likelihood estimation is considered and the computational algorithms discussed. A data set from Goodman (1981) and another from Gabriel and Zamir (1979) are used to demostrate the diagnostic rules.     

The need for new statistical legislation for the UK

Summary. The paper is written to inform public discussion on whether or not statistical legislation for the UK is needed and, if so, on its nature and content. A brief account of the background to the current position is given. The Government's stated intention is to create an 'independent statistical service' and a discussion of the meaning of independence in the context of official stat- istics and governance arrangements is provided. Recent international experience is described and the Statistics Acts of some other countries are used to distil the key features of Statistics Acts in other countries. The arguments for and against possible legislation are described. Whether or not a Statistics Act is desirable for the UK depends strongly on the legislation being well framed. There are several key issues on which Parliament would need to develop an informed view and these are set out towards the end of the paper.     

A Proposal for a New Bound for Discrete Distributions

In this work we re-examine some classical bounds for non negative integer-valued random variables by means of information theoretic or maxentropic techniques using fractional moments as constraints. The proposed new bound, no more analytically expressible in terms of moments or moment generating function (mgf), is built by mixing classical bounds and the Maximum Entropy (ME) approximant of the underlying distribution; such a new bound is able to exploit optimally all the information content provided by the sequence of given moments or by the mgf. Particular care will be devoted to obtain fractional moments from the available information given in terms of integer moments and/or moment generating function. Numerical examples show clearly that the bound improvement involving the ME approximant based on fractional moments is not trivial.