Exact sample size determination in a weibull test plan when there is time censoring

Engineers who conduct reliability tests need to choose the sample size when designing a test plan. The model parameters and quantiles are the typical quantities of interest. The large-sample procedure relies on the property that the distribution of the t -like quantities is close to the standard normal in large samples. In this paper, we use a new procedure based on both simulation and asymptotic theory to determine the sample size for a test plan. Unlike the complete data case, the t -like quantities are not pivotal quantities in general when data are time censored. However we show that the distribution of the t -like quantities only depend on the expected proportion failing and obtain the distributions by simulation for both complete and time censoring case when data follow Weibull distribution. We find that the large-sample procedure usually underestimates the sample size even when it is said to be 200 or more. The sample size given by the proposed procedure insures the requested nominal accuracy and confidence of the estimation when the test plan results in complete or time censored data. Some useful figures displaying the required sample size for the new procedure are also presented.     

因子模型门槛效应的LM和Wald检验及其统计性质研究

门槛因子模型可以有效地刻画高维度时间序列的共变特征和区制转换行为,具有良好的可解释性和预测能力。针对因子载荷矩阵存在的门槛效应,本文提出了拉格朗日乘子和沃尔德检验方法,并给出了渐近分布,相关结果表明以上检验统计量具有良好的大样本性质和有限样本表现。在实证部分,以我国股市的行业指数作为研究对象,通过构建门槛因子模型来刻画我国股票市场波动的共变性特征和非对称效应。实证结果表明基于门槛因子模型可以很好地刻画中国股市行业收益率波动的共变特征和区制转换行为。     

In-Sample Inference and Forecasting in Misspecified Factor Models

This article considers in-sample prediction and out-of-sample forecasting in regressions with many exogenous predictors. We consider four dimension-reduction devices: principal components, ridge, Landweber Fridman, and partial least squares. We derive rates of convergence for two representative models: an ill-posed model and an approximate factor model. The theory is developed for a large cross-section and a large time-series. As all these methods depend on a tuning parameter to be selected, we also propose data-driven selection methods based on cross-validation and establish their optimality. Monte Carlo simulations and an empirical application to forecasting inflation and output growth in the U.S. show that data-reduction methods outperform conventional methods in several relevant settings, and might effectively guard against instabilities in predictors’ forecasting ability.     

论影响民族地区法治建设的因素——以四川凉山州彝族自治州为例

中华人民共和国是一个以汉族为主体,还有55个少数民族组成的统一的单一制国家。在少数民族聚居地方,实行民族区域自治,从而实现各民族团结、平等、进步和共同繁荣。依法治国方略,在西部民族地区仍然是实施该地区繁荣进步的基本策略。在西部大开发及加入WTO的大环境下,如何优化民族地区的发展环境,趋利避害,抓住机遇,发展经济,客观上也要求民族地区应有一个良好的法制环境。西部民族地区的法治建设,应充分考虑到各少数民族的历史、经济、人文、宗教、习惯等因素。     

A Factor-Adjusted Multiple Testing Procedure With Application to Mutual Fund Selection

In this article, we propose a factor-adjusted multiple testing (FAT) procedure based on factor-adjusted p-values in a linear factor model involving some observable and unobservable factors, for the purpose of selecting skilled funds in empirical finance. The factor-adjusted p-values were obtained after extracting the latent common factors by the principal component method. Under some mild conditions, the false discovery proportion can be consistently estimated even if the idiosyncratic errors are allowed to be weakly correlated across units. Furthermore, by appropriately setting a sequence of threshold values approaching zero, the proposed FAT procedure enjoys model selection consistency. Extensive simulation studies and a real data analysis for selecting skilled funds in the U.S. financial market are presented to illustrate the practical utility of the proposed method. Supplementary materials for this article are available online.     

A misspecification test for the higher order co-moments of the factor model

The traditional estimation of higher order co-moments of non-normal random variables by the sample analog of the expectation faces a curse of dimensionality, as the number of parameters increases steeply when the dimension increases. Imposing a factor structure on the process solves this problem; however, it leads to the challenging task of selecting an appropriate factor model. This paper contributes by proposing a test that exploits the following feature: when the factor model is correctly specified, the higher order co-moments of the unexplained return variation are sparse. It recommends a general to specific approach for selecting the factor model by choosing the most parsimonious specification for which the sparsity assumption is satisfied. This approach uses a Wald or Gumbel test statistic for testing the joint statistical significance of the co-moments that are zero when the factor model is correctly specified. The asymptotic distribution of the test is derived. An extensive simulation study confirms the good finite sample properties of the approach. This paper illustrates the practical usefulness of factor selection on daily returns of random subsets of S&P 100 constituents.     

要素匹配与中国投资效率空间差异性——基于双层嵌套型函数的分解研究

本文基于四要素双层嵌套的生产函数,利用1990-2016年全国层面及省际层面数据测算投资效率,并分析其空间结构特征及演变轨迹,检验投资效率匹配效应影响因素。研究发现：①1990-2016年我国整体投资效率呈下降趋势,资本-技能劳动匹配效应与整体投资效率走势趋同,快速累积的资本存量和不断升级的资本质量与短缺的技能劳动之间矛盾突出。②东中西部地区投资效率增长非一致性明显。东部地区资本相对投资效率明显高于中西部,但下降幅度大于中西部,中西部与东部地区之间差距缩小,其中匹配效应是区域间投资效率非平衡的主要成因。③若产业结构升级的技能劳动需求不能满足,将引发要素错配,不利于有效投资。房价与工资提升分别通过影响技能劳动供给和需求抑制要素匹配效率;教育和公路设施会对地区要素匹配产生积极影响,改善地区间投资效率非均衡性;地区投资效率存在显著正向空间相关性,毗邻地区的要素流动和经济发展相近地区的技术溢出均对投资效率产生积极的影响。     

大学生社会文化价值观特征分析

一个民族的文化通常有其系统性与适用的价值观,在当今中西文化交融的时代背景下,作为未来栋梁的大学生选择何种价值观体系,一直受到学术界的普遍关注。借鉴相关价值观研究理论,通过因子分析的方法,归纳出大学生的7个价值观类型,并揭示出大学生社会文化价值观的主要特征,即儒家思想中的进取精神得到了大学生的普遍认同,而极端功利与利己主义受到大学生的强烈排斥,大学生的"自我意识"呈现出不统一的特点,实用主义观念在大学生中广泛存在,传统价值观中的"节俭观"和"宿命论"在大学生中受到了严峻的挑战。     

我国制造业集聚变迁与全要素生产率增长研究

本文选取我国29个省市区和17个制造行业1990～2009年的面板数据,对相对专业化与相对多样化集聚度进行了计算及变迁分析,利用Malmquist指数测算了全要素生产率的增长,并分析了产业集聚变迁对全要素生产率的影响。结果表明:我国东部地区呈现多样化与专业化集聚均衡发展的特征,而中西部地区则具有相对较高的专业化集聚水平,呈现产业结构单一化与非均衡化;东部地区全要素生产率增长较快,中西部地区相对滞后;相对专业化与多样化集聚对东部、中部与西部地区的影响存在地区差异。基于此,本文提出了加快产业结构调整、实施均衡的区域发展政策和提高经济组织制度绩效的政策建议。     

基于因子分析的产学研合作教育影响因素研究

本文通过构建产学研合作教育影响因素的指标体系,运用因子分析法导出其中的主要影响因素,通过多元回归分析,进一步厘清各因子的影响程度,提出促进产学研合作教育人才培养机制的对策建议。