Progressive type II censored order statistics from exponential distributions

In the model of progressive type II censoring, point and interval estimation as well as relations for single and product moments are considered. Based on two-parameter exponential distributions, maximum likelihood estimators (MLEs), uniformly minimum variance unbiased estimators (UMVUEs) and best linear unbiased estimators (BLUEs) are derived for both location and scale parameters. Some properties of these estimators are shown. Moreover, results for single and product moments of progressive type II censored order statistics are presented to obtain recurrence relations from exponential and truncated exponential distributions. These relations may then be used to compute all the means, variances and covariances of progressive type II censored order statistics based on exponential distributions for arbitrary censoring schemes. The presented recurrence relations simplify those given by Aggarwala and Balakrishnan (1996)     

Strong consistency of presmoothed Kaplan–Meier integrals when covariables are present

It is known that the Kaplan–Meier estimation may be improved via presmoothing methods. In this article, we introduce an extended presmoothed Kaplan–Meier estimator in the presence of covariates. The main result is the strong consistency of general empirical integrals based on such an estimator. As applications, one can obtain a consis-tent multivariate empirical distribution under censoring, and also can obtain a consistent estimation of regression parameters. We illustrate the new estimation methods through simulations and real data analysis.     

Semiparametric score test for varying copula parameter in Markov time series

This article examines a semiparametric test for checking the constancy of serial dependence via copula models for Markov time series. A semiparametric score test is proposed for testing the constancy of the copula parameter against stochastically varying copula parameter. The asymptotic null distribution of the test is established. A semiparametric bootstrap procedure is employed for the estimation of the variance of the proposed score test. Illustrations are given based on simulated series and historic interest rate data.     

Does Low Willingness to Respond Introduce a Bias? Results from a Socio-epidemiological study among Young Men and Women

The aim of this study was to investigate if willingness to respond can introduce bias in a population survey and to study the socio-economic characteristics of those with high and low willingness to respond. Two groups of final-year pupils at compulsory school were surveyed five years after leaving school, at the age of 21. The data were collected during class meetings, by mailed questionnaires, telephone and personal interviews. The response rates in the studies were proportionally high – about 98% and 90% respectively. In both surveys there were more men compared to women who were late respondents or non-respondents. Long-term unemployment and lack of upper secondary school for both men and women, as well as living with a partner for men, corresponded to low willingness to respond to a survey. A higher alcohol consumption – between 1.5 to 6.5 times – was observed among those with lower willingness to respond. Even a low rate of non-response can introduce a serious bias and produce uncertain results in, for example, studies on the consequences of youth unemployment on alcohol consumption.     

The zero-inflated Poisson model and the decayed, missing and filled teeth index in dental epidemiology

For frequency counts, the situation of extra zeros often arises in biomedical applications. This is demonstrated with count data from a dental epidemiological study in Belo Horizonte (the Belo Horizonte caries prevention study) which evaluated various programmes for reducing caries. Extra zeros, however, violate the variance–mean relationship of the Poisson error structure. This extra-Poisson variation can easily be explained by a special mixture model, the zero-inflated Poisson (ZIP) model. On the basis of the ZIP model, a graphical device is presented which not only summarizes the mixing distribution but also provides visual information about the overall mean. This device can be exploited to evaluate and compare various groups. Ways are discussed to include covariates and to develop an extension of the conventional Poisson regression. Finally, a method to evaluate intervention effects on the basis of the ZIP regression model is described and applied to the data of the Belo Horizonte caries prevention study.     

转基因生物安全立法的动力、压力、阻力探析

法律的制定是一系列力量共同作用的结果,其中既有动力,也有压力和阻力。认真厘清和分析转基因生物安全立法的动力、压力和阻力,有利于推进转基因生物安全的立法进程、提高转基因生物安全法的立法质量。     

Estimating the error distribution function in semiparametric additive regression models

We consider semiparametric additive regression models with a linear parametric part and a nonparametric part, both involving multivariate covariates. For the nonparametric part we assume two models. In the first, the regression function is unspecified and smooth; in the second, the regression function is additive with smooth components. Depending on the model, the regression curve is estimated by suitable least squares methods. The resulting residual-based empirical distribution function is shown to differ from the error-based empirical distribution function by an additive expression, up to a uniformly negligible remainder term. This result implies a functional central limit theorem for the residual-based empirical distribution function. It is used to test for normal errors.     

Sorting people out: The uses of one-dimensional classificatory schemes in a multi-dimensional world

This paper examines how people are classified as part of a labour market project aimed at establishing a process for recognizing prior learning among immigrants to Sweden in order to integrate them more quickly with the labour market and society. The paper suggests that, in Sweden, this work prioritizes procedural effectiveness over a more comprehensive understanding of the competence and qualifications of the immigrant worker. By exploring the process of classification in which cognitive structuring of the perceived world results in organizational, administrative and structural enactment, the study provides further insights into how practices of classification are a central part of organizational life. The concept of intersectionality contributes by showing how individuals are situated at the intersection of a variety of classificatory schemes, and together with classification, intersectionality points to how organizational categories are never given, but a result of bureaucratic power procedures strengthening, weakening and/or negotiating away categories used to sort people out.     

Waivers of parental consent for sexual minority youth

ABSTRACT

The Society for Adolescent Health and Medicine emphasizes the need for research to focus on the health outcomes of sexual minority youth (i.e., lesbian, gay, bisexual, transgender, queer). However, sexual minority youth (SMY) are often less willing to participate in research studies where parental consent is required due to potential victimization and discrimination. This is a major concern given that more research is needed to understand the health needs of this population, especially in terms of suicide, substance use, and HIV prevention. The National Suicide Prevention Strategy classifies SMY as a high-risk group, emphasizing the need to explore suicide risks (along with other health outcomes) among this group. However, this high-risk classification also increases the safeguards necessary to conduct research with this population. Many researchers have argued for waivers of parental consent, but such waivers present with several ethical implications. This article discusses ethical principles, risks, benefits, safeguards, and potential alternative approaches to waivers of parental consent for SMY. We conclude by emphasizing the need for policy changes to allow parental consent waivers for research targeting SMY.