Model averaging for treatment effect estimation in subgroups

In many clinical trials, biological, pharmacological, or clinical information is used to define candidate subgroups of patients that might have a differential treatment effect. Once the trial results are available, interest will focus on subgroups with an increased treatment effect. Estimating a treatment effect for these groups, together with an adequate uncertainty statement is challenging, owing to the resulting “random high” / selection bias. In this paper, we will investigate Bayesian model averaging to address this problem. The general motivation for the use of model averaging is to realize that subgroup selection can be viewed as model selection, so that methods to deal with model selection uncertainty, such as model averaging, can be used also in this setting. Simulations are used to evaluate the performance of the proposed approach. We illustrate it on an example early‐phase clinical trial.     

On Modeling Wood Formation Using Parametric and Semiparametric Regressions for Count Data

Understanding how wood develops has become an important problematic of plant sciences. However, studying wood formation requires the acquisition of count data difficult to interpret. Here, the annual wood formation dynamics of a conifer tree species were modeled using generalized linear and additive models (GLM and GAM); GAM for location, scale, and shape (GAMLSS); a discrete semiparametric kernel regression for count data. The performance of models is evaluated using bootstrap methods. GLM was useful to describe the wood formation general pattern but had a lack of fitting, while GAM, GAMLSS, and kernel regression had a higher sensibility to short-term variations.     

黄山市音乐考级的现状调查与研究

音乐考级是对音乐能力进行的分级考试。黄山市作为皖南山城,具有浓厚的徽州文化底蕴,在当地老百姓的观念中学习艺术是旁门左道,自从十年前第一个音乐考级点建立起,至今已有三个考级单位,参与培训并获得考级证书的学员近万人。极大程度上推动了黄山市素质教育的发展,更新了老百姓的传统观念。本文通过对黄山市音乐考级现状的调查与分析,了解本市音乐考级这一机制的运行情况,总结音乐考级带来的成效以及存在的不良发展趋向,提出解决弊端的方法并对黄山市音乐考级未来发展提出建设性的建议。     

Assessment of study abroad outcomes in Chinese as a second language: gains in cross-cultural adaptability,language contact and proficiency

Participants were 109 American college students studying Chinese in a study-abroad programme in Beijing. Following Kelley and Meyer, intercultural competence was defined as cross-cultural adaptability involving four dimensions (emotional resilience, flexibility/openness, perceptual acuity and personal autonomy) and was measured with a survey. A language contact questionnaire was used to document the amount of time spent on social activities. Language proficiency was measured with a standardised Chinese test. Results revealed that intercultural competence and language contact combined explained 37.7% of the proficiency gains. Language contact had direct effects on proficiency, but intercultural competence had indirect effects, mediated by language contact.     

Adaptive stochastic gradient boosting tree with composite criterion

ABSTRACT

In this paper, we propose an adaptive stochastic gradient boosting tree for classification studies with imbalanced data. The adjustment of cost-sensitivity and the predictive threshold are integrated together with a composite criterion into the original stochastic gradient boosting tree to deal with the issues of the imbalanced data structure. Numerical study shows that the proposed method can significantly enhance the classification accuracy for the minority class with only a small loss in the true negative rate for the majority class. We discuss the relation of the cost-sensitivity to the threshold manipulation using simulations. An illustrative example of the analysis of suboptimal health-state data in traditional Chinese medicine is discussed.     

基于动物秉性的人生启示*

动物和人一样，也具有不同的秉性。以动物喻人，自古即有。从辩证的角度看，动物秉性自然有好的一面，也有坏的一面。这里我们借助动物思考人生，专门探讨动物秉性中一些好的品质，狗-无比忠诚；猪-难得糊涂；狼-勇敢合作的典范；牛-勤劳奉献精神；狐狸-聪明智慧的象征；龟-勤恳踏实的榜样。可见，动物的许多秉性亦给人生带来诸多的启示，值得人们以思考和学习。     

Least squares estimation of varying‐coefficient hazard regression with application to breast cancer dose‐intensity data

To enhance modeling flexibility, the authors propose a nonparametric hazard regression model, for which the ordinary and weighted least squares estimation and inference procedures are studied. The proposed model does not assume any parametric specifications on the covariate effects, which is suitable for exploring the nonlinear interactions between covariates, time and some exposure variable. The authors propose the local ordinary and weighted least squares estimators for the varying‐coefficient functions and establish the corresponding asymptotic normality properties. Simulation studies are conducted to empirically examine the finite‐sample performance of the new methods, and a real data example from a recent breast cancer study is used as an illustration. The Canadian Journal of Statistics 37: 659–674; 2009 © 2009 Statistical Society of Canada     

Modes of Practice and the Dual Mission of Social Work

Abstract

This study examines the commitment of social work in various countries to its declared dual missionenhancing individual well-being and promoting social justice. It does so by examining the mode of practice preferences of graduating BSW students from seven countries. Based on cluster analysis, three distinct subgroups of students with particular patterns of preferences were found: a generic group, a direct/micro group, and a macro group. The distribution of students among these groups differs between country cohorts. While each of the clusters was to be found in all the countries studied, in three country cohorts, a majority of students belonged to the generic group and a considerable number sought to engage in macro practice, reflecting a commitment to the profession's dual focus. The majority of the students within the remaining country cohorts preferred micro practice and were far less willing to adopt macro level practices.     

有效提高远程学习者自主学习的策略

本文通过对远程学习者自主学习的现状分析，提出相应的策略以帮助学员更有效地开展和提高远程自主学习。