The Appropriateness of Some Common Procedures for Testing the Equality of Two Independent Binomial Populations

For testing the equality of two independent binomial populations the Fisher exact test and the chi-squared test with Yates's continuity correction are often suggested for small and intermediate size samples. The use of these tests is inappropriate in that they are extremely conservative. In this article we demonstrate that, even for small samples, the uncorrected chi-squared test (i.e., the Pearson chi-squared test) and the two-independent-sample t test are robust in that their actual significance levels are usually close to or smaller than the nominal levels. We encourage the use of these latter two tests.     

Robust estimation in the generalized poisson model

A computationally simple method of robust estimation in the generalized Poisson model is presented. Estimators are proved to be optimal in the sense of local minimax testing, conditionally on the explanatory variable. Results of a Monte Carlo experiment are supplemented where robust and efficient estimators are compared.     

Regression model with elliptically contoured errors

For the regression model y=X β+ε where the errors follow the elliptically contoured distribution, we consider the least squares, restricted least squares, preliminary test, Stein-type shrinkage and positive-rule shrinkage estimators for the regression parameters, β.

We compare the quadratic risks of the estimators to determine the relative dominance properties of the five estimators.     

Pension scheme fees and charge ratios in 44 countries: A comparative study

Based on data received from pension supervisory authorities, the article reviews 85 different pension schemes in 44 jurisdictions by looking at fees and charges as well as their legal ceilings and their development since 2014. A key finding is the observed decrease in fees and caps. The article presents jurisdictions according to clusters, i.e. by groups of countries with identical or very similar items already covered by pension fees, and analyses the extent to which various cost and fee elements are covered by fees charged to members. Finally, we calculate charge ratios for each cluster to quantify the impact of fees and charges on pension savings. Occupational defined contribution pension schemes and personal plans linked to employment tend to be much more cost effective than personal schemes that have no direct employment link.     

我国客户关系管理研究的紧迫性和方向分析

客户关系管理(CRM ) 是当前的研究热点. 由于国内企业发展的特殊轨迹, 在此方面的研 究和应用明显落后于国外. 针对这种情况, 本文在分析客户关系管理的内涵及其意义的基础 上, 详细阐述了中国加强这一领域研究与应用的重要性和紧迫性, 并探索了国内研究的具体 方向.     

How Large Are Your G-Values? Try Gosset’s Guinnessometrics When a Little “p” Is Not Enough

Abstract

A crisis of validity has emerged from three related crises of science, that is, the crises of statistical significance and complete randomization, of replication, and of reproducibility. Guinnessometrics takes commonplace assumptions and methods of statistical science and stands them on their head, from little p-values to unstructured Big Data. Guinnessometrics focuses instead on the substantive significance which emerges from a small series of independent and economical yet balanced and repeated experiments. Originally developed and market-tested by William S. Gosset aka “Student” in his job as Head Experimental Brewer at the Guinness Brewery in Dublin, Gosset’s economic and common sense approach to statistical inference and scientific method has been unwisely neglected. In many areas of science and life, the 10 principles of Guinnessometrics or G-values outlined here can help. Other things equal, the larger the G-values, the better the science and judgment. By now a colleague, neighbor, or YouTube junkie has probably shown you one of those wacky psychology experiments in a video involving a gorilla, and testing the limits of human cognition. In one video, a person wearing a gorilla suit suddenly appears on the scene among humans, who are themselves engaged in some ordinary, mundane activity such as passing a basketball. The funny thing is, prankster researchers have discovered, when observers are asked to think about the mundane activity (such as by counting the number of observed passes of a basketball), the unexpected gorilla is frequently unseen (for discussion see Kahneman 2011 Kahneman, D. (2011), Thinking Fast and Slow, New York: Farrar, Straus and Giroux. [Google Scholar]). The gorilla is invisible. People don’t see it.     

论《英雄不过是三明治》的叙事特色

美国黑人女作家爱丽丝·奇尔德里斯的小说《英雄不过是三明治》主要有两个叙事特点,一是使用多人第一人称视角观察和叙述故事,二是在相应章节间穿插新闻、广告等非虚构材料,把虚构文本和纪实文本融为一体,为表现小说的主题提供了有力的支撑,使小说具有鲜明的叙事特色和独到的艺术效果。     

Detection of multiple undocumented change-points using adaptive Lasso

The problem of detecting multiple undocumented change-points in a historical temperature sequence with simple linear trend is formulated by a linear model. We apply adaptive least absolute shrinkage and selection operator (Lasso) to estimate the number and locations of change-points. Model selection criteria are used to choose the Lasso smoothing parameter. As adaptive Lasso may overestimate the number of change-points, we perform post-selection on change-points detected by adaptive Lasso using multivariate t simultaneous confidence intervals. Our method is demonstrated on the annual temperature data (year: 1902–2000) from Tuscaloosa, Alabama.     

On the Properties of the Likelihood Function of Spanos' Conditional t Heteroskedastic Model

This article investigates the properties of the likelihood function of Spanos’ conditional t heteroskedastic model (Spanos, 1994 Spanos , A. ( 1994 ). On modeling heteroskedasticity: The student's t and elliptical linear regression models . Econometric Theor. 10 : 286 – 315 .[Crossref], [Web of Science ®] , [Google Scholar]) On modeling heteroskedasticity: the student's t and elliptical linear regression models. It is shown that estimability of the degrees of freedom of t distribution and the block-diagonality of the information matrix of the joint likelihood function with respect to conditional mean parameters and remaining parameters hold for the model. The joint maximum likelihood estimator and its inference based on the t-statistic and χ²-statistic are examined in finite samples by simulation when the degrees of freedom is known and unknown.     

Moment-Implied Densities: Properties and Applications

Suppose one uses a parametric density function based on the first four (conditional) moments to model risk. There are quite a few densities to choose from and depending on which is selected, one implicitly assumes very different tail behavior and very different feasible skewness/kurtosis combinations. Surprisingly, there is no systematic analysis of the tradeoff one faces. It is the purpose of the article to address this. We focus on the tail behavior and the range of skewness and kurtosis as these are key for common applications such as risk management.