A robust coefficient of determination for regression

To assess the quality of the fit in a multiple linear regression, the coefficient of determination or R² is a very simple tool, yet the most used by practitioners. Indeed, it is reported in most statistical analyzes, and although it is not recommended as a final model selection tool, it provides an indication of the suitability of the chosen explanatory variables in predicting the response. In the classical setting, it is well known that the least-squares fit and coefficient of determination can be arbitrary and/or misleading in the presence of a single outlier. In many applied settings, the assumption of normality of the errors and the absence of outliers are difficult to establish. In these cases, robust procedures for estimation and inference in linear regression are available and provide a suitable alternative.     

国际资本流动冲击有利于经济增长吗

本文估算并应用潜在产出描述经济增长,尝试从国际合作角度设定动态结构面板向量自回归模型,识别自发性国际资本流动的综合性结构冲击,并进一步分解为共同冲击和特有冲击,提出研究国际资本流动冲击对经济增长影响的计量思路,以金砖国家为例进行实证分析。研究发现：国际资本流动冲击对金砖各国经济增长的效应因资本账户开放进程而异,但对金砖整体经济增长存在正效应,且不为金砖各国之间的资本流动冲击所扰;将金砖国家视为以国际合作形式联合的整体进行计量分析是可行且有经济意义的。中国应推进包括金砖国家在内的全方位南南合作,不断完善资本账户开放条件,分散国际资本流动冲击并使其有利于长期共同发展。     

Modelling Variability in the Branching Structure of Strawberry Inflorescences

The branching structure of inflorescences of the cultivated strawberry ( Fragaria × ananassa Duch.) is very variable. This paper demonstrates that some aspects of this variability are well described by a simple stochastic model of branching that has two adjustable parameters. The model is shown to provide a good fit to data from a set of almost 700 inflorescences of the cultivar Elsanta, collected over two successive years. For one parameter the maximum likelihood estimator is a moment estimator which is fully efficient even if the detailed branching structure of the inflorescences is not recorded. This parameter provides a convenient summary of branching vigour. The maximum likelihood estimator of the second parameter must be determined iteratively and can be quite inefficient unless the full branching structure is recorded. The model demonstrates that branching structure is affected by the order in which inflorescences emerge on the plant.     

威布尔分布场合步加试验和步降试验的效率比较分析

 本文通过大量的Monte-Carlo模拟,在四个不同的准则下就威布尔分布比较了步进应力加速寿命试验和步降应力加速寿命试验的效率,认为步降应力加速寿命试验很值得推广,尤其是针对耗损型产品。     

企业技术效率的影响分析

 本文以上海市166家大中型企业五年的面板数据为研究对象,设定两种不同的生产函数和两种误差分布,利用随机前沿方法分别进行了技术效率的估计。我们发现不同测算方法的结果差异不大,且对企业的评价具有一致性。结果表明上海市工业企业的技术效率整体水平不高。通过研究影响企业技术效率的外生性因素,发现企业的所有制结构、规模、R&D经费支出与R&D人员投入、资本密集程度和企业的垄断程度等因素都对上海市工业企业的技术效率水平具有显著影响。基于研究结果,我们给出了提高企业技术效率的一些建议。     

A note on Läuter-type robust design for polynomial regression models

In this paper, we consider the problem of model robust design for simultaneous parameter estimation among a class of polynomial regression models with degree up to k. A generalized D-optimality criterion, the Ψ_α‐optimality criterion, first introduced by Läuter (1974) is considered for this problem. By applying the theory of canonical moments and the technique of maximin principle, we derive a model robust optimal design in the sense of having highest minimum Ψ_α‐efficiency. Numerical comparison indicates that the proposed design has remarkable performance for parameter estimation in all of the considered rival models.     

ROW AND COLUMAN DESIGNS WITH CONTIGUOUS REPLICATES

A method is given for constructing row and column designs for situations where replicates are contiguous. Designs of this type are needed in cotton variety trials. A table of generating arrays is given from which a series of resolvable designs can be constructed; these designs are called latinized α-designs. Some results from cotton variety trials are presented.     

The predictability of stock returns - a nonparametric approach

This paper reexamines the predictability of stock returns with a nonparametric model. We first identify, through a set of diagnostic tests, five lagged predictive factors from a linear model. Using these factors, we predict one-month-ahead stock index returns with a nonparametric approach. We find that our nonparametricmodel. We first identify, through a set of diagnostic tests, five lagged predictive factors from a linear model. Using these factors, we predict on -month-ahead stock index returns with a nonparametric approach. We find that our nonparametric model can correctly predict about 74% of stock index return signs. With various ex ante trading rules based on nonparametric predictions and transaction cost schedules, we then compare the performance of "managed" portfolios with that of the buy and hold portfolios. We fmd that the managed portfolios are mean-variance dominant over the buy-and-hold strategies when no or low transaction costs are assumed. When high transaction costs are assumed instead, the mean-variance dominance diminishes However,the Sharpe index of risk-adjusted portfolio performanceindicates that the managed portfolios significantly outperform the buy-and-hold strategies even for the high-transaction cost scenario. We show that the difference in performance between the managed portfolios and the buy-and-hold strategies can be partially explained by the January effect or the small firm effect. In sum, this paper demonstrates the merits of using a nonparametric approach for predicting stock returns and testing market efficiency.     

行政管理革新与法治政府建设——应以法治和发展的眼光审视当下的行政管理新举措

当下深化改革的进程中我国行政管理新举措层出不穷且争议甚多,可从几个方面加以观察和评价:一是诸多典型案(事)例暴露出严重的观念滞后问题,必须克服戴旧眼镜看新事物的现象;二是内容丰富的行政管理改革创新是在宏大复杂的背景下进行的,最主要的背景因素是经济和政治改革的深化和科技革命的影响;三是我国行政管理改革创新的动向,是以人为本前提下走向柔性管理、高效管理和方法创新,重点是行政管理方式方法的创新发展,相对而言这是成本低、风险小、效率高、成效稳健、易达共识的路径选择;四是行政管理改革创新应坚持法治原则和实践标准等基本界限,防止借创新之名行营私之实。当下关键在于我们要以法治和发展的眼光去看待、宽容和冷静的心态去对待这些行政管理改革的创新举措。     

提高大学英语大班课效率刍议

随着高等教育的扩招，高校普遍在非英语专业大学英语课程中采用了大班教学模式以解决师资短缺的矛盾，由此也出现了一系列的问题。在本文中，作者以本人及所在学校的教学实践为例，论述了在大班教学中所存在的问题及其解决办法。笔者认为，作为大学英语教师，只要转变观念，努力认识大班教学的规律，提高大班教学的效率是有可能的。