Estimation Procedure for a Multiple Time Series Model

Given a multiple time series sharing common autoregressive patterns, we estimate an additive model. The autoregressive component and the individual random effects are estimated by integrating maximum likelihood estimation and best linear unbiased predictions in a backfitting algorithm. The simulation study illustrated that the estimation procedure provides an alternative to the Arellano–Bond generalized method of moments (GMM) estimator of the panel model when T > N and the Arellano–Bond generally diverges. The estimator has high predictive ability. In cases where T ≤ N, the backfitting estimator is at least comparable to Arellano–Bond estimator.     

混合题型的IRT等值问题研究

我们称既有0—1评分题,又有多级评分题的试卷为混合题型试卷,简称为混合题型．以往国内对混合题型的测验等值采用的方法是将Logistic模型看成是等级反应模型或拓广的分部评分模型的特例,这种处理方式就可能忽略了项目的猜测因素．为了解决这一问题,本文将三参数的Logistic模型和GRM进行扩展得到混合模型,并针对此模型开发了相应的等值程序．另外,为了检验某次测验0—1评分项目存在猜测,而人为将其忽略所带来的误差大小,本文进行了大量的MonteCarlo模拟实验．实验结果表明,若某测验中0—1评分项目存在猜测而等值时忽略这一事实误用GRM,在绝大部分情况下都比用混合模型等值的误差大而且有显著性差异,并且等值的误差会随着猜测度的的增大而增大．     

Mixed Liu estimator in linear measurement error models

In this paper, we introduce mixed Liu estimator (MLE) for the vector of parameters in linear measurement error models by unifying the sample and the prior information. The MLE is a generalization of the mixed estimator (ME) and Liu estimator (LE). In particular, asymptotic normality properties of the estimators are discussed, and the performance of the MLE over the LE and ME are compared based on mean squared error matrix (MSEM). Finally, a Monte Carlo simulation and a numerical example are also presented for analysis.     

中国对“一带一路”沿线国家出口持续期及影响因素研究

“一带一路”倡议提出后,中国对沿线国家的出口贸易总量已经有所突破。与此同时产品出口是否也变得更加稳定？出口贸易的稳定性决定贸易联系的长期发展,稳定的贸易联系有利于中国企业的稳定发展。本文利用高度细分且重复观测的出口纵向生存数据,利用Cox随机效应混合模型进行两种时期的对比研究,并在模型中考虑交互作用。研究发现,“一带一路”倡议提出后,总体上,向沿线各国出口贸易更加稳定,各地区差距明显缩小,高技术产品出口稳定性显著提升,技术型产品与非技术型产品拉开了差距,出口产品结构有所优化。同时,倡议的提出对于GDP或人均GDP较低国家的出口稳定性推动最明显,尤其体现在技术型产品上。“一带一路”倡议提出后,出口贸易几乎不受汇率波动影响,倡议的提出在一定程度上削弱了远距离对出口的不利影响,且较大的初始贸易额所带来的优势对高技术产品出口稳定性的促进作用最明显。双边贸易联系的紧密性体现得更明显,而且双边贸易联系越紧密越有利于技术型产品出口。     

基于混频数据的实体经济与金融市场时变溢出效应研究

本文基于混频VAR模型分析了中国实体经济与股票市场、债券市场之间的时变溢出效应。结果显示,实体经济与股票市场、债券市场之间收益率与波动率的溢出效应呈现显著的时变特征,溢出效应在金融危机期间呈现快速上升趋势,而后呈现下降态势,且易受到极端事件的影响;在大部分考察时期内存在股票市场向实体经济的波动率溢出效应,而债券市场相对于实体经济则从考察初期波动率溢出效应的净输入方转化为中后期的波动率溢出效应的净输出方。进一步分析收益率与波动率总溢出指数的影响因素,结果发现,极端事件、宏观经济代理变量和期限利差对于溢出效应具有正向影响,泰德利差对波动率总溢出指数具有负向影响,而投资者情绪指数对收益率总溢出指数具有负向影响。     

Visualizing uncertainty in reliability functions with application to aero engine overhaul

Summary.  We propose an approach for estimating the date of lost confidence of jet engines, which are devices with multiple components subject to disruption. A mixed Weibull distribution is estimated from a large data set subject to censoring at various times. Parametric uncertainty is derived analytically and mapped visually onto the functions of use in reliability theory, including the hazard function. We demonstrate the use of the method on a database of disruption times for components in 325 jet engines.     

What are Children's Centres? The Development of CC Services, 2004–20081

Children's centres are intended to be a mainstream, universal service. They began in 2004 and their origins are diverse. Some replaced various forms of local provision, most notably Sure Start programmes; others were established from scratch. Issues for exploratory empirical work have been identified from the guidance issued by central government. Using interview data from three urban local authorities, this article explores the nature of the ‘core offer’ that centres are expected to provide and the way in which they have pursued the goal of integrating staff and services. The article highlights the problems of balancing a focus on the child and on the parent; of reconciling childcare provision as part of the employability agenda and as a means to educational achievement for the child; of permitting local variation while achieving consistency; of the role of monitoring in relation to developing good practice; and of achieving integration in a mixed economy of care. We find that despite the greater specification of the core offer for children's centres compared to that for Sure Start, there are substantial differences between children's centres in terms of services, while the mixed economy of provision poses considerable challenges to the goal of integration.     

A comparison of inference procedures in unbalanced split-plot designs

Several procedures for constructing confidence intervals and testing hypotheses about fixed effects in unbalanced split-plot experiments are described in this paper. These procedures can also be used for unbalanced repeated measures experiments when the repeated measures satisfy the Huyhn-Feldt (1970) conditions. A number of these procedures require that the whole plot error mean square has a distribution proportional to a chi-square distribution and that it be independent of estimators of the parameter functions. Often, neither of these conditions are met in unbalanced split-plot experiments. Simulation studies of a small design of eight observations and larger designs with 34 to 48 observations are used to investigate the performance of the different procedures.     

The Analysis of Designed Experiments and Longitudinal Data by Using Smoothing Splines

In designed experiments and in particular longitudinal studies, the aim may be to assess the effect of a quantitative variable such as time on treatment effects. Modelling treatment effects can be complex in the presence of other sources of variation. Three examples are presented to illustrate an approach to analysis in such cases. The first example is a longitudinal experiment on the growth of cows under a factorial treatment structure where serial correlation and variance heterogeneity complicate the analysis. The second example involves the calibration of optical density and the concentration of a protein DNase in the presence of sampling variation and variance heterogeneity. The final example is a multienvironment agricultural field experiment in which a yield–seeding rate relationship is required for several varieties of lupins. Spatial variation within environments, heterogeneity between environments and variation between varieties all need to be incorporated in the analysis. In this paper, the cubic smoothing spline is used in conjunction with fixed and random effects, random coefficients and variance modelling to provide simultaneous modelling of trends and covariance structure. The key result that allows coherent and flexible empirical model building in complex situations is the linear mixed model representation of the cubic smoothing spline. An extension is proposed in which trend is partitioned into smooth and non-smooth components. Estimation and inference, the analysis of the three examples and a discussion of extensions and unresolved issues are also presented.