中国股票市场风险因素的相关性研究

近年来国外关于资本资产定价模型(CAPM)的实证研究不断对该模型提出严厉的质疑,其中很多研究认为除了贝塔系数外,市值size、账面市值比be/me、市盈率p/e这三个风险因素都对股票的收益率具有一定的解释能力。然而这些风险因素能否独立地解释股票的收益率还没有定论。就因素本身来说,size与p/e之间存在较强的相关性,而be/me与其余两因素之间几乎不存在相关性。就因素对投资组合收益率的解释能力来说,p/e几乎不具有独立的解释能力,size的独立解释能力最强,而be/me在较大公司中有一定的独立解释能力。     

软件开发项目工作量估算技术的比较研究

软件开发项目的工作量估算技术一般分为三类:基于专家判断的技术、基于算法模型的技术和面向学习的技术.不同的估算技术各有自己的优点和局限性,没有一种估算技术能适用于所有开发环境,并且软件开发方法和技术的更新速度也对所有这些估算技术提出了挑战.软件组织应根据具体的项目特征和可获得的信息来选择合适的估算技术,并针对当前项目情况对使用的估算模型加以调整,依据不同技术的特点组合不同的估算技术进行估算,以提高估算准确性.在估算项目工作量时要充分考虑到项目前期阶段的工作量,并建立本组织的软件项目库.     

A simple variance formula for population size estimators by conditioning

This note considers the variance estimation for population size estimators based on capture–recapture experiments. Whereas a diversity of estimators of the population size has been suggested, the question of estimating the associated variances is less frequently addressed. This note points out that the technique of conditioning can be applied here successfully which also allows us to identify sources of variation: the variance due to estimation of the model parameters and the binomial variance due to sampling n units from a population of size N. It is applied to estimators typically used in capture–recapture experiments in continuous time including the estimators of Zelterman and Chao and improves upon previously used variance estimators. In addition, knowledge of the variances associated with the estimators by Zelterman and Chao allows the suggestion of a new estimator as the weighted sum of the two. The decomposition of the variance into the two sources allows also a new understanding of how resampling techniques like the Bootstrap could be used appropriately. Finally, the sample size question for capture–recapture experiments is addressed. Since the variance of population size estimators increases with the sample size, it is suggested to use relative measures such as the observed-to-hidden ratio or the completeness of identification proportion for approaching the question of sample size choice.     

Sequential Procedure For Fixed Accuracy Estimation of the Population Size in Recapture Sampling

A sequential procedure is constructed to provide a fixed‐accuracy estimator for the number of faults in a system. This paper focuses on the case when faults are homogeneous. However, the method can be adapted to other models by choosing a more robust estimator. The accuracy of the estimator depends on the failure intensity, the length of testing period and the total number of faults in the system. Simulations illustrate the performance of the proposed procedure. The method is applied to an information system failure dataset.     

Estimation and Extrapolation of Tumor Probabilities from a Mouse Bioassay with Survival/Sacrifice Components

A nonparametric estimator of the probability distribution of time-to-tumor is incorporated into an algorithm for calculating linearly extrapolated dosage limits from an animal carcino-genesis bioassay. The procedure is illustrated with tumor data from a mouse bioassay with 2-acetylaminofluorene. Extrapolated dosage limits for an excess risk of 10^-6 differ by only a factor of 2 across the six replicates of the experiment.     

Inference Based on Conditional Moment Inequalities

In this paper, we propose an instrumental variable approach to constructing confidence sets (CS's) for the true parameter in models defined by conditional moment inequalities/equalities. We show that by properly choosing instrument functions, one can transform conditional moment inequalities/equalities into unconditional ones without losing identification power. Based on the unconditional moment inequalities/equalities, we construct CS's by inverting Cramér–von Mises‐type or Kolmogorov–Smirnov‐type tests. Critical values are obtained using generalized moment selection (GMS) procedures. We show that the proposed CS's have correct uniform asymptotic coverage probabilities. New methods are required to establish these results because an infinite‐dimensional nuisance parameter affects the asymptotic distributions. We show that the tests considered are consistent against all fixed alternatives and typically have power against n^−1/2‐local alternatives to some, but not all, sequences of distributions in the null hypothesis. Monte Carlo simulations for five different models show that the methods perform well in finite samples.     

论城镇化背景下小规模幼儿园的合理性——基于小规模幼儿园不合法性的反思

城镇化是当今中国社会变迁的重要特征,并将持续到未来的几十年之后,市民化是城镇化的核心。在城镇化进程中小规模幼儿园具有必然的合理性,具有＂广覆盖、保基本＂的普惠性质,对满足社会弱势群体的多元学前教育需求具有重要价值。认识误区和政策歧视使具有平民性质的小规模幼儿园被排斥在体制之外,遭遇合理性与不合法性的剧烈冲突。地方政府需要反思政绩观,转变政策理念,从底层民众的立场出发采用多种政策工具发展小规模幼儿园。     

陕北白绒山羊体尺指标与生产性能的多元统计模型简

研究陕北白绒山羊体尺指标与生产性能之间的关系,确定产绒量与体重、体长、体高、胸围、管围之间的线性相关关系,应用相关分析、多元线性回归、逐步回归、主成分分析等统计方法,借助SPSS等软件的数据分析功能,建立生产性能与体尺指标之间的最优回归模型,为陕北白绒山羊品种的选育、羊绒产量的提高提供良好的建议。     

基于城市流理论的甘肃省中心城市规模等级结构优化研究

运用城市流强度的测定方法,计算甘肃省12座地级城市的外向型功能量、城市流强度和城市流倾向度,依据各城市的城市流强度值将城镇体系规模等级结构划分为3个层次:一级中心城市为兰州,其城市流强度值最高,是省内经济集聚和扩散的中心;二级中心城市为酒泉和庆阳,其城市流强度值较低,是省内次级辐射中心;三级中心城市为平凉、定西、陇南、天水、白银、武威、金昌、张掖和嘉峪关,城市流强度值极低,是地方集聚与辐射的中心。最后,依据各城市的城市流强度结构,提出甘肃省中心城市城市流的强化对策和规模等级结构的优化建议。