Two-stage hierarchical modeling for analysis of subpopulations in conditional distributions

In this work, we develop modeling and estimation approach for the analysis of cross-sectional clustered data with multimodal conditional distributions where the main interest is in analysis of subpopulations. It is proposed to model such data in a hierarchical model with conditional distributions viewed as finite mixtures of normal components. With a large number of observations in the lowest level clusters, a two-stage estimation approach is used. In the first stage, the normal mixture parameters in each lowest level cluster are estimated using robust methods. Robust alternatives to the maximum likelihood estimation are used to provide stable results even for data with conditional distributions such that their components may not quite meet normality assumptions. Then the lowest level cluster-specific means and standard deviations are modeled in a mixed effects model in the second stage. A small simulation study was conducted to compare performance of finite normal mixture population parameter estimates based on robust and maximum likelihood estimation in stage 1. The proposed modeling approach is illustrated through the analysis of mice tendon fibril diameters data. Analyses results address genotype differences between corresponding components in the mixtures and demonstrate advantages of robust estimation in stage 1.     

从冯梦龙对柳永形象的重塑看话本小说的文人化——以《众名姬春风吊柳七》对《柳耆卿诗酒玩江楼记》的改编为例

从《清平山堂话本》到“三言”,文人的参与对话本小说的发展起着至关重要的作用。以《众名姬春风吊柳七》对《柳耆卿诗酒玩江楼记》的改编为例,冯梦龙从体制、情节、语言等方面对柳永形象作了一番重塑,藉此也观见了话本小说发展史中文人化的轨迹：对话本小说体制的完善和定型化,思想主题的升华,人物形象塑造艺术的圆熟,教化性的强化,语言的雅化。     

将城市的记忆融入现代城市生活——论伊宁六星街历史街区的保护与发展策略

历史街区是城市发展的历史见证和缩影,有着深厚的文化积淀。这些悠久的历史遗迹随着时光的河流汇聚成为城市文脉,也印证着每个城市独特的风貌。本文以新疆伊宁市六星街为例,探讨在城市的发展中那些记录着时代变迁的历史街区的重要性及其保护与发展。     

论柳永对宋代山水词的贡献

柳永对宋代山水词的发展贡献甚大,他翻新民间慢词俗曲和自创慢词新调,为山水景物的铺写提供了有效的载体,并且因其山水景物题材的诗意化,使得慢词雅化,山水景物成为他"雅"的那部分作品的重要元素;他铺写山水园林景物的词,扩展了白居易、潘阆的描绘手段,更加细致生动;他刻画羁旅行役中的旅途风光以抒怀,铺叙展衍,积累了以词写旅途山水景物、情景交融的经验。他写山水园林风貌以及行旅途中的山水景物而展扩的词境,走出了传统词的写景狭小逼仄的天地,为山水词的进一步发展做了极有意义的开拓。     

基于企业价值与发行特征的定向增发定价效率研究

近年来,定向增发逐渐成为上市公司增发的主流方式.与公开增发相比,定向增发具有不同的发行特点.在考虑企业价值的基础上,引入发行特征这一因素,将定向增发新股的定价视作一个生产过程,运用随机前沿分析方法,对非效率项的分布假设进行扩展,以此来分析定向增发的定价效率,并以2006年4月至2009年10月的定向增发企业为样本展开实证研究.实证结果表明,中国上市公司定向增发的定价效率有待提高,企业价值和发行特征等相关因素对发行定价效率有着不同程度和方向的影响.     

大城市中心效应地位与城市交通拥堵问题

交通拥堵是城市化发展的一种派生物,不仅仅是交通系统自身的问题。治理交通拥堵需要分散交通流。然而大城市分散交通流缓解城市交通拥堵的同时,又需要不与提高城市竞争力的目标相违背。通过分析分散交通流的主要途径,进一步探究大城市中心地位的形成、多中心与公司总部、中心城市与功能混合以及中心地之间的轨道交通连接等问题。当城市按照产业集聚形成不同的多中心布局后,有效的功能混合将减少交通流的产生,轨道交通的连接将分担道路交通流的压力。     

Small area estimation of mean price of habitation transaction using time-series and cross-sectional area-level models

In this paper, a new small domain estimator for area-level data is proposed. The proposed estimator is driven by a real problem of estimating the mean price of habitation transaction at a regional level in a European country, using data collected from a longitudinal survey conducted by a national statistical office. At the desired level of inference, it is not possible to provide accurate direct estimates because the sample sizes in these domains are very small. An area-level model with a heterogeneous covariance structure of random effects assists the proposed combined estimator. This model is an extension of a model due to Fay and Herriot [5], but it integrates information across domains and over several periods of time. In addition, a modified method of estimation of variance components for time-series and cross-sectional area-level models is proposed by including the design weights. A Monte Carlo simulation, based on real data, is conducted to investigate the performance of the proposed estimators in comparison with other estimators frequently used in small area estimation problems. In particular, we compare the performance of these estimators with the estimator based on the Rao–Yu model [23]. The simulation study also accesses the performance of the modified variance component estimators in comparison with the traditional ANOVA method. Simulation results show that the estimators proposed perform better than the other estimators in terms of both precision and bias.     

Optimal Composite Markers for Time‐Dependent Receiver Operating Characteristic Curves with Censored Survival Data

Abstract. To increase the predictive abilities of several plasma biomarkers on the coronary artery disease (CAD)‐related vital statuses over time, our research interest mainly focuses on seeking combinations of these biomarkers with the highest time‐dependent receiver operating characteristic curves. An extended generalized linear model (EGLM) with time‐varying coefficients and an unknown bivariate link function is used to characterize the conditional distribution of time to CAD‐related death. Based on censored survival data, two non‐parametric procedures are proposed to estimate the optimal composite markers, linear predictors in the EGLM model. Estimation methods for the classification accuracies of the optimal composite markers are also proposed. In the article we establish theoretical results of the estimators and examine the corresponding finite‐sample properties through a series of simulations with different sample sizes, censoring rates and censoring mechanisms. Our optimization procedures and estimators are further shown to be useful through an application to a prospective cohort study of patients undergoing angiography.     

Testing for order among K populations: theory and examples

Testing for stochastic order among K populations is a common and important problem in statistical practice. It arises in the analysis of both planned experiments and observational studies. The authors develop a new nonparametric test for order among K populations that can accommodate any stochastic ordering. The test is based on a maximally selected chi‐bar‐square statistic. The authors find its limiting distribution and use simulations to derive critical values. Three important examples are used to illustrate the applicability of the general method. The authors find that the new tests outperform the existing methods in many practical cases. The Canadian Journal of Statistics 38: 97–115; 2010 © 2009 Statistical Society of Canada     

v至诚的革命者？优秀的文学家？—对柳青及《创业史》的再认识之二

作为革命者的柳青,他是合格的,是值得人们尊敬的,但是作为艺术家的柳青,则是有严重之不足的。他自觉地进行思想改造,其结果是令自己成为了至诚的革命者;他长期地深入生活,其结果是令自己更坚定地为元产阶级政治服务;他遭遇“文革”的灾难,其结果是令自己固守“生活本位”的文学观念;他晚年对《创业史》进行了修改,其的结果是把自己的创作进一步推向了概念化和虚假化。