Perfect simulation for correlated Poisson random variables conditioned to be positive

In this paper we present a perfect simulation method for obtaining perfect samples from collections of correlated Poisson random variables conditioned to be positive. We show how to use this method to produce a perfect sample from a Boolean model conditioned to cover a set of points: in W.S. Kendall and E. Thönnes (Pattern Recognition 32(9): 1569–1586, 1999), this special case was treated in a more complicated way. The method is applied to several simple examples where exact calculations can be made, so as to check correctness of the program using ²-tests, and some small-scale experiments are carried out to explore the behaviour of the conditioned Boolean model.     

反命名和戏谑式命名——杨绛散文的反讽修辞

杨绛散文的反讽修辞对应着两个语境 :故事发生时的语境 ( 5 0年代初至 70年代初 )和故事写作时的语境 ( 80 - 90年代 )。她将“陪斗者”这一政治身份转化为叙述人的观察和言说视角 ,通过“反命名和戏谑式命名”的修辞方式 (表现为“我不是…”/“我是…”的语式 ) ,实现了对语境限制的反限制 ,构成了一种“互文本”的深层意义结构。其戏谑式命名的常用方式是“贬低陈述”。作为女性写作 ,杨绛选择反讽作为自己散文的基本修辞方式 ,既是时间的积累沉淀对她的话语启示 ,也是她对自己文化素质审美心智优长的一种发挥     

Social comparison,group identity and professional identity. A study with bank clerks

Abstract

This study consisted of analyzing several hypotheses derived from Tajfel and Turner's social identity theory (Tajfel and Turner, 1979) within a real-life situation. We identified the intergroup relations among three banks in Brazil as an ideal chance to test the salience hypothesis (Oakes & Turner, 1980; Doise & Sinclair, 1973) and also the relationship between discrimination and social identity (Brown et al. 1983b). In general, results did not support the hypotheses, and alternative explanations of results, in terms of the groups ' real life conditions, are discussed.     

A General Multivariate Threshold GARCH Model With Dynamic Conditional Correlations

We introduce a new multivariate GARCH model with multivariate thresholds in conditional correlations and develop a two-step estimation procedure that is feasible in large dimensional applications. Optimal threshold functions are estimated endogenously from the data and the model conditional covariance matrix is ensured to be positive definite. We study the empirical performance of our model in two applications using U.S. stock and bond market data. In both applications our model has, in terms of statistical and economic significance, higher forecasting power than several other multivariate GARCH models for conditional correlations.     

Monte carlo evidence on the robustness of conditional moment tests in tobit and probit models

This paper numerically examines the size robustness of various conditional moment tests in misspecified tobit and probit models. The misspecifications considered include the incorrect exclusion of regressors, ignored heteroskedasticity and false distributional assumptions. An important feature of the experimental design is that it is based on an existing empirical study and is more realistic than many simulation studies. The tests are seen to have mixed performance depending on both the original null hypothesis being tested and type of misspecification encountered.     

Censored Kullback-Leibler Information and Goodness-of-Fit Test with Type II Censored Data

The Kulback-Leibler information has been considered for establishing goodness-of-fit test statistics, which have been shown to perform very well (Arizono & Ohta, 1989; Ebrahimi et al., 1992, etc). In this paper, we propose censored Kullback-Leibler information to generalize the discussion of the Kullback-Leibler information to the censored case. Then we establish a goodness-of-fit test statistic based on the censored Kullback-Leibler information with the type 2 censored data, and compare the test statistics with some existing test statistics for the exponential and normal distributions.     

Gaussian copula distributions for mixed data,with application in discrimination

The construction of a joint model for mixed discrete and continuous random variables that accounts for their associations is an important statistical problem in many practical applications. In this paper, we use copulas to construct a class of joint distributions of mixed discrete and continuous random variables. In particular, we employ the Gaussian copula to generate joint distributions for mixed variables. Examples include the robit-normal and probit-normal-exponential distributions, the first for modelling the distribution of mixed binary-continuous data and the second for a mixture of continuous, binary and trichotomous variables. The new class of joint distributions is general enough to include many mixed-data models currently available. We study properties of the distributions and outline likelihood estimation; a small simulation study is used to investigate the finite-sample properties of estimates obtained by full and pairwise likelihood methods. Finally, we present an application to discriminant analysis of multiple correlated binary and continuous data from a study involving advanced breast cancer patients.     

Tests for Equality of Parameters of Two Exponential Distributions with Common Known Coefficient of Variation

ABSTRACT

This article considers the problem of testing equality of parameters of two exponential distributions having common known coefficient of variation, both under unconditional and conditional setup. Unconditional tests based on BLUE'S and LRT are considered. Using the Conditionality Principle of Fisher, an UMP conditional test for one-sided alternative is derived by conditioning on an ancillary. This test is seen to be uniformly more powerful than unconditional tests in certain given ranges of ancillary. Simulation studies on the power functions of the tests are done for this purpose.     

A stepwise discrete variable selection procedure

A stepwise variable selection procedure for multinomial discrimination is presented and discussed. Based upon the work of Kullback and Hills, stopping rules are proposed and illustrated for a set of data on communication buyer behavior.     

动态需求下高峰负荷定价模型研究

针对Ｍａｃｈａｅｌ．Ｒ关于动态需求下高峰负荷定价过于理想化假设的问题，建立了新的调控定价模型，并进行了具体的分析，得到不同阶段应采取不同的定价策略，培育和引导了消费市场，由此深化了Ｍａｃｈａｅｌ．Ｒ的结论。