ROBUSTNESS OF PROCEDURES FOR THE BEHRENS-FISHER PROBLEMS: EXTENSION TO BIVARIATE NORMAL MIXTURES

In the applied sciences, it is often important to be able to compare the mean values of two populations. However, testing a hypothesis can be complex, if the two populations are heteroscedastic and exhibit non-normality in the data. This paper reviews currently available strategies for the multivariate Behrens-Fisher problem. It then carries out Monte Carlo comparisons of selected procedures to assess their robustness when applied to data from normal mixture distributions. The overall conclusion is that Johansen's procedure appears to work best for small sample data both in terms of empirical power and significance level. Johansen's procedure works reasonably well even with mixture data. The simulation also provides researchers with specific guidelines to follow at the early designing and planning stages of the investigation.     

论类型学的定义与范畴

探讨类型学的实质及其研究范围,以寻求真正适合国内教学与研究实践的类型学理论极具意义。文章梳理了国内比较文学教材对类型学的定义,发现大多只强调类同性的研究,而忽视对异质性的关注。在这一理论的指导下,中国大多数类型学研究只强调求同。这与俄苏的历史类型学求同存异的学术旨趣是不同的。曹顺庆教授提倡类型学的异质研究,既是对俄苏历史类型学研究思路的回归,更偏重于寻求不同文化的异质性。类型学异质研究是第三世界国家在跨文明语境下开展类型学类同研究陷入困境时的一种努力,这对构建民族自信心,维护世界多元文化和谐的生态环境有积极的意义。本文认为真正完整而有可操作性的类型学研究应该包括两个步骤：先进行类同研究,然后再进行异质研究。     

Acute Middle Ear Infection in Small Children: A Bayesian Analysis Using Multiple Time Scales

The study is based on a sample of 965 children living in Oulu region (Finland), who were monitored for acute middle ear infections from birth to the age of two years. We introduce a nonparametrically defined intensity model for ear infections, which involves both fixed and time dependent covariates, such as calendar time, current age, length of breast-feeding time until present, or current type of day care. Unmeasured heterogeneity, which manifests itself in frequent infections in some children and rare in others and which cannot be explained in terms of the known covariates, is modelled by using individual frailty parameters. A Bayesian approach is proposed to solve the inferential problem. The numerical work is carried out by Monte Carlo integration (Metropolis-Hastings algorithm).     

企业异质性与贸易中介理论研究新进展

新新贸易理论诞生近十年来,贸易理论家围绕企业异质性假定进行了细致而富有成效的拓展研究。其中引人注目的是融入贸易中介的分析,打破了已有研究关于直接出口的局限,并分别基于异质性和企业内生边界视角,解释了中介技术和不完全合约对企业直接出口和中介出口等不同出口决策及福利分配的影响。本文梳理了国外最新文献中企业异质性与贸易中介理论的研究进展,解析了将贸易中介引入新新贸易理论的微观机理,并展望了其未来的发展方向。     

The consequences of unobserved heterogeneity in a sequential logit model

Cameron and Heckman (1998) established that a sequential logit model is more sensitive than many other models to the possible biasing influence of unobserved heterogeneity. This article proposes a method which allows researchers to find out how large this potential problem is for their data, their model, and their hypothesis of interest. This is done by proposing a set of scenarios for this unobserved heterogeneity, and showing how to estimate the effects of interest given these scenarios. The set of results from these scenarios give an indication of how sensitive the results are to assumptions regarding unobserved heterogeneity. This sensitivity analysis has been applied to a study of educational attainment in the Netherlands, and it showed that that the finding that the effect of father's education declined over transitions is quite sensitive to the assumptions made about unobserved heterogeneity, but that the finding that the effect of father's education declined over birth cohorts is more robust than is often feared.     

Modeling Endogenous Mobility in Earnings Determination

ABSTRACT

We evaluate the bias from endogenous job mobility in fixed-effects estimates of worker- and firm-specific earnings heterogeneity using longitudinally linked employer–employee data from the LEHD infrastructure file system of the U.S. Census Bureau. First, we propose two new residual diagnostic tests of the assumption that mobility is exogenous to unmodeled determinants of earnings. Both tests reject exogenous mobility. We relax exogenous mobility by modeling the matched data as an evolving bipartite graph using a Bayesian latent-type framework. Our results suggest that allowing endogenous mobility increases the variation in earnings explained by individual heterogeneity and reduces the proportion due to employer and match effects. To assess external validity, we match our estimates of the wage components to out-of-sample estimates of revenue per worker. The mobility-bias-corrected estimates attribute much more of the variation in revenue per worker to variation in match quality and worker quality than the uncorrected estimates. Supplementary materials for this article are available online.     

台湾诗歌对后现代主义的接受与变形

台湾诗歌在 80年代对西方后现代主义文学的选择和接受具有一种历史必然性 ,这使得台湾诗歌典范发生了三种变动 ,即 :反纯粹性的本文混杂 ;反深度的事物本原化 ;反确定性的语符游戏。由于受时代的、民族精神的和文化心理的影响 ,台湾诗歌理论与创作又呈现了在特殊接受语境中发生的变异 ,即 :台湾诗人对“本体”的怀疑是一种方法论意义上的怀疑 ;他们将语义的不确定性往往归结于语言本身的局限性     

E-optimal designs for three treatments

E-optimality is studied for three treatments in an arbitrary n-way heterogeneity setting. In some cases maximal trace designs cannot be E-optimal. When there is more than one E-optimal design for a given setting, the best with respect to all reasonable criteria is determined.     

Methods for exploring treatment effect heterogeneity in subgroup analysis: an application to global clinical trials

Multi‐country randomised clinical trials (MRCTs) are common in the medical literature, and their interpretation has been the subject of extensive recent discussion. In many MRCTs, an evaluation of treatment effect homogeneity across countries or regions is conducted. Subgroup analysis principles require a significant test of interaction in order to claim heterogeneity of treatment effect across subgroups, such as countries in an MRCT. As clinical trials are typically underpowered for tests of interaction, overly optimistic expectations of treatment effect homogeneity can lead researchers, regulators and other stakeholders to over‐interpret apparent differences between subgroups even when heterogeneity tests are insignificant. In this paper, we consider some exploratory analysis tools to address this issue. We present three measures derived using the theory of order statistics, which can be used to understand the magnitude and the nature of the variation in treatment effects that can arise merely as an artefact of chance. These measures are not intended to replace a formal test of interaction but instead provide non‐inferential visual aids, which allow comparison of the observed and expected differences between regions or other subgroups and are a useful supplement to a formal test of interaction. We discuss how our methodology differs from recently published methods addressing the same issue. A case study of our approach is presented using data from the Study of Platelet Inhibition and Patient Outcomes (PLATO), which was a large cardiovascular MRCT that has been the subject of controversy in the literature. An R package is available that implements the proposed methods. Copyright © 2014 John Wiley & Sons, Ltd.     

"异质"≠"神秘"——评索绪尔的语言"同质"观

言语是"活"的语言,它是语言的导向,也是思维的导向。时空的变异、社会的异质及主体的人文性决定了言语的异质性,但"异质"≠"神秘"。言语符号的不断重复与组合呈现一定的规律与制度,是探索语言本质、语言变化机制和预测语言规律等的很好契机。语言与言语没有自然界限,水乳交融,因而语言也不可能是"同质"的。