Asymptotics of cross-validated risk estimation in estimator selection and performance assessment

Risk estimation is an important statistical question for the purposes of selecting a good estimator (i.e., model selection) and assessing its performance (i.e., estimating generalization error). This article introduces a general framework for cross-validation and derives distributional properties of cross-validated risk estimators in the context of estimator selection and performance assessment. Arbitrary classes of estimators are considered, including density estimators and predictors for both continuous and polychotomous outcomes. Results are provided for general full data loss functions (e.g., absolute and squared error, indicator, negative log density). A broad definition of cross-validation is used in order to cover leave-one-out cross-validation, V-fold cross-validation, Monte Carlo cross-validation, and bootstrap procedures. For estimator selection, finite sample risk bounds are derived and applied to establish the asymptotic optimality of cross-validation, in the sense that a selector based on a cross-validated risk estimator performs asymptotically as well as an optimal oracle selector based on the risk under the true, unknown data generating distribution. The asymptotic results are derived under the assumption that the size of the validation sets converges to infinity and hence do not cover leave-one-out cross-validation. For performance assessment, cross-validated risk estimators are shown to be consistent and asymptotically linear for the risk under the true data generating distribution and confidence intervals are derived for this unknown risk. Unlike previously published results, the theorems derived in this and our related articles apply to general data generating distributions, loss functions (i.e., parameters), estimators, and cross-validation procedures.     

心理辅导综合模式及其实践意义

心理辅导综合模式是以生活生涯发展理论为基础构建的一种全新的学校心理辅导模式。它将心理辅导与教学视为两种同等重要的教育传输系统,明确规定心理辅导教师的工作内容,注重心理辅导的综合性与发展性,强调心理辅导应面向全体学生,面向学生社会生活并促进学生能力的全面发展。心理辅导综合模式是当代美国最有影响的学校心理辅导模式。这一模式对改进我国学校心理辅导工作具有借鉴意义。     

Cp准则应用于遴选最佳ANOVA模型

以往在对特定的方差分析（ANOVA）资料指定其数学模型时，都是根据因子及因子之间的互作效应的多少来进行的，似乎在ANOVA问题当中不存在模型选择问题。本文则表明在ANOVA当中不但存在着模型选择问题，而且利用Cp准则还能导致正确的结论。     

冬季育雏卫生防疫工作模式化管理的推广应用

以哲里木盟与呼伦贝尔盟部分养鸡场、鸡农户的四种不同品种鸡为试验对象，推广一整套在实践探索中表现良好防疫效果的卫生防疫体系，经5个月的推广试验取得了重复性较高的防疫效果，使育雏率平均由87％提高到97.6％。     

SIOP模式及其对我国双语教学的启示

SIOP模式是教授英语学习者学科内容的一种教学模式,还是课堂观察的评价工具,其主要包括八大组成部分和三十条细则。该模式目前广泛运用于美国中小学教学之中,并取得了理想的效果。SIOP模式对我国双语教学具有以下三点启示:我国双语教学应以实践为导向、理论为指导、课堂为中心、学生为主体;我国双语教学应兼顾内容目标和语言目标;我国双语教学需要开发具有很高信度和效度的双语课堂教学评价工具。     

Online Intermediary as a Channel for Selling Quality‐Differentiated Services

When deciding whether to utilize an online intermediary in addition to their own distribution channels, quality differentiated service providers face the trade‐off between the benefit of extended reach and the threat of increased competition. Using an analytical framework, we analyze when and how service providers may utilize an online intermediary to their advantage in the presence of advance selling (i.e., selling a service at an early date for future consumption). In general, when an online intermediary is used, the competition effect dominates the reach effect and leads to a falling price trend. Interestingly, we find that the negative effect of increased competition on profits, due to intermediary usage, can be reversed by committing to self‐imposed participation limits (i.e., selling only a predetermined amount of services through the online intermediary). This ensures that the service provider is better off selling through both its own site and the online intermediary, rather than selling exclusively using either channel.      

基于神经网络的产品创新项目风险评估方法研究

产品创新是企业在现代市场环境下经济增长的主要方式,但产品创新项目具有很高的风险性和不确定性,产品创新项目的风险管理己成为学术界和企业界所关注的重要研究课题。文章拟对产品创新项目风险评估问题进行较为系统的分析,研究基于产品创新管理的产品创新项目风险评价指标体系及基于神经网络的产品创新项目风险评估模型,为产品创新项目风险评估提供新的理论基础和方法论。     

英语强化训练可行性的理论探讨

本文从回顾英语强化教学的发展历程入手,探讨语言强化教学模式在教学法及其上位学科语言学、教育学、心理学等方面的理论依据,并以此对广东培正学院实行的英语强化训练教学模式的特点进行分析和研究,从理论上探讨实施英语强化训练教学模式的可行性。     

城市边缘化社区聚居模式初探——桃浦七村实地调查的思考

本文结合对一个城市边缘化社区的实地调查,综合分析了边缘化社区居民的生活习惯和聚居模式,并在此基础上提出有针对性的住区规划和建筑方面的对策;最后讨论了边缘社区的聚居模式和阶层混居之间的关系.