Verification bias on sensitivity and specificity measurements in diagnostic medicine: a comparison of some approaches used for correction

Verification bias may occur when the test results of not all subjects are verified by using a gold standard. The correction for this bias can be made using different approaches depending on whether missing gold standard test results are random or not. Some of these approaches with binary test and gold standard results include the correction method by Begg and Greenes, lower and upper limits for diagnostic measurements by Zhou, logistic regression method, multiple imputation method, and neural networks. In this study, all these approaches are compared by employing a real and simulated data under different conditions.     

Goodness-of-fit tests based on the distance between the Dirichlet process and its base measure

The Dirichlet process is a fundamental tool in studying Bayesian nonparametric inference. The Dirichlet process has several sum representations, where each one of these representations highlights some aspects of this important process. In this paper, we use the sum representations of the Dirichlet process to derive explicit expressions that are used to calculate Kolmogorov, Lévy, and Cramér–von Mises distances between the Dirichlet process and its base measure. The derived expressions of the distance are used to select a proper value for the concentration parameter of the Dirichlet process. These tools are also used in a goodness-of-fit test. Illustrative examples and simulation results are included.     

Covariate Decomposition Methods for Longitudinal Missing‐at‐Random Data and Predictors Associated with Subject‐Specific Effects

Investigators often gather longitudinal data to assess changes in responses over time within subjects and to relate these changes to within‐subject changes in predictors. Missing data are common in such studies and predictors can be correlated with subject‐specific effects. Maximum likelihood methods for generalized linear mixed models provide consistent estimates when the data are ‘missing at random’ (MAR) but can produce inconsistent estimates in settings where the random effects are correlated with one of the predictors. On the other hand, conditional maximum likelihood methods (and closely related maximum likelihood methods that partition covariates into between‐ and within‐cluster components) provide consistent estimation when random effects are correlated with predictors but can produce inconsistent covariate effect estimates when data are MAR. Using theory, simulation studies, and fits to example data this paper shows that decomposition methods using complete covariate information produce consistent estimates. In some practical cases these methods, that ostensibly require complete covariate information, actually only involve the observed covariates. These results offer an easy‐to‐use approach to simultaneously protect against bias from both cluster‐level confounding and MAR missingness in assessments of change.     

Nexus及其在英汉文学翻译中的应用

junction 和nexus 是丹麦语言学家Otto Jespersen 提出的一对语言学概念.Jespersen认为一个首品词(primary)和一个附着语(adjunct)组合成一个偏正结构(junction),而一个首品词(primary)和一个谓语(predicate)组合成一个主谓结构 (nexus).Junction 是一个意义的合成,只表达一个意义;Nexus则包含两个意义.Jespersen对比二者得出结论:junction 就好比一幅画,而nexus则是一个过程,一出戏;前者较为呆板,缺乏生气,后者却灵活生动,富于生机.本文着重比较了junction和nexus的不同之处,进而讨论了nexus在英汉文学翻译中的应用,以期在实践中验证nexus的优势.     

通过课堂互动减少大学校园里的偏见和歧视

偏见和歧视是社会心理学中的两个概念,在学习过程中,采用课堂讨论这种互动方式,使同学们跳出书本内容的局限,从知识的概念、社会现实中的表现、产生的原因、如何减少偏见和歧视这四个方面去理解和探索,师生共同探讨减少偏见和歧视的方法,可达到减少大学校园里同学之间存在的偏见和歧视的效果.     

Sexual Orientation and Quality of Life Among University Students from Cuba,Norway, India,and South Africa

This article explores quality-of-life aspects among gay, lesbian, bisexual, and straight male and female students in Havana (Cuba), Troms? (Norway), Hisar (India), and Cape Town (South Africa). In the period 2004–2005, a questionnaire survey on sexuality, happiness, and life satisfaction was undertaken among 339 students from the University of Havana, 144 students from the University of Troms?, 200 students from Guru Jambheswar University, and 189 students from the University of the Western Cape. The majority of the participants were straight and, in Hisar and Cape Town, few of those who regarded themselves as gay/lesbian/bisexual had engaged in sex with a person of the same gender. In all cities, straight men and women scored higher than gay, lesbian, and bisexual persons on the quality-of-life measures. Quality of life among gay/bisexual men and lesbian/bisexual women was higher in cultures with accepting attitudes toward homosexuality than in cultures with restrictive attitudes.     

人口老龄化的区域经济效应分析——基于新古典经济增长模型

人口老龄化与区域经济发展之间有着必然的内在关联性。因为生产和消费是区域经济发展中的重要环节,而人口老龄化对生产和消费均有影响,也就必然会影响区域经济的发展。因此,本文首先在梳理国内外相关研究的基础上提出人口老龄化对区域经济发展的双重效应——正效应和负效应;然后以新古典经济增长模型为基础,尝试引入人口老龄化因素从而对该模型进行扩展,分析得到的结论是:①进一步验证了人口老龄化对区域经济发展的双重效应的存在;②不同的区域,人口老龄化程度不同,人口再生产所处于的发展阶段不同,人口老龄化对区域经济发展的经济影响程度,即其正效应和负效应之和也就不尽相同,但存在的一个基本规律是,人口老龄化程度越高,其负效应就越大,其对区域经济发展的减速效应也就越明显。     

养老金正常调整机制与养老负担关系分析

我国自建立城镇职工社会养老保险制度之初就提出要对养老金进行正常调整,但在近20年的实际操作过程中,仍未建立起统一、稳定、科学的调整机制。本文首先分析了在人口老龄化的背景下,养老金调整机制与养老负担之间的定量关系,根据现收现付制度的运行机理和经济增长原理分别推导出两种不同养老金调整机制下维持养老负担不变的临界条件,以我国人口老龄化趋势预测为基础对临界条件进行实证检验后得出结论,即在保持养老负担不变的前提下,不同的养老金调整机制对于经济增长率和工资增长率具有不同要求。文章为我国养老金调整机制的完善提供一定的依据。     

Test for Trend With a Multinomial Outcome

ABSTRACT

There is no established procedure for testing for trend with nominal outcomes that would provide both a global hypothesis test and outcome-specific inference. We derive a simple formula for such a test using a weighted sum of Cochran–Armitage test statistics evaluating the trend in each outcome separately. The test is shown to be equivalent to the score test for multinomial logistic regression, however, the new formulation enables the derivation of a sample size formula and multiplicity-adjusted inference for individual outcomes. The proposed methods are implemented in the R package multiCA.     

Estimating and testing effect size from an arbitrary population

In this article, we develop inference tools for an effect size parameter in a paired experiment. A class of estimators is defined that includes natural, shrinkage and shrinkage preliminary test estimators. The shrinkage and preliminary test methods incorporate uncertain prior information on the parameter. This information may be available in the form of a realistic guess on the basis of the experimenter’s knowledge and experience, which can be incorporated into the estimation process to increase the efficiency of the estimator. Asymptotic properties of the proposed estimators are investigated both analytically and computationally. A simulation study is also conducted to assess the performance of the estimators for moderate and large samples. For illustration purposes, the method is applied to a data set.