Identifying Guttman Structures in Incomplete Rasch Datasets

In applications of IRT, it often happens that many examinees omit a substantial proportion of item responses. This can occur for various reasons, though it may well be due to no more than the simple fact of design incompleteness. In such circumstances, literature not infrequently refers to various types of estimation problem, often in terms of generic “convergence problems” in the software used to estimate model parameters. With reference to the Partial Credit Model and the instance of data missing at random, this article demonstrates that as their number increases, so does that of anomalous datasets, intended as those not corresponding to a finite estimate of (the vector parameter that identifies) the model. Moreover, the necessary and sufficient conditions for the existence and uniqueness of the maximum likelihood estimation of the Partial Credit Model (and hence, in particular, the Rasch model) in the case of incomplete data are given – with reference to the model in its more general form, the number of response categories varying according to item. A taxonomy of possible cases of anomaly is then presented, together with an algorithm useful in diagnostics.     

Testing homogeneity of difference of two proportions for stratified correlated paired binary data

In ophthalmologic or otolaryngologic study, each subject may contribute paired organs measurements to the analysis. A number of statistical methods have been proposed on bilateral correlated data. In practice, it is important to detect confounding effect by treatment interaction, since ignoring confounding effect may lead to unreliable conclusion. Therefore, stratified data analysis can be considered to adjust the effect of confounder on statistical inference. In this article, we investigate and derive three test procedures for testing homogeneity of difference of two proportions for stratified correlated paired binary data in the basis of equal correlation model assumption. The performance of proposed test procedures is examined through Monte Carlo simulation. The simulation results show that the Score test is usually robust on type I error control with high power, and therefore is recommended among the three methods. One example from otolaryngologic study is given to illustrate the three test procedures.     

时间趋势平稳性检验的带宽选择及其影响

本文将基于最小化两类错误的概率选择带宽的思想引入KPSS检验。文章通过蒙特卡罗仿真实验,对基于最小化均方误差和最小化两类错误概率的KPSS检验的有限样本性质进行了比较;并对中国季度实际GDP对数序列的平稳性进行了检验。结果表明,基于最小化两类错误概率的检验比基于最小化均方误差的检验有更大的水平扭曲,但前者也有更大的检验势;并且在误差项自回归系数小于等于0.5的大多数情形下,基于最小化两类错误概率的检验有更好的有限样本性质;中国季度实际GDP对数序列是带漂移的单位根过程。     

Do healthy diets in Europe matter to the environment? A quantitative analysis

Final consumption of food products figures amongst the strongest contributors to negative environmental impacts in Europe, with the production of beef and pork at agricultural level being the main responsible part of the food supply chain. This article analyses quantitatively the environmental impact of changing European diets. The environmental impact of European consumption is determined with an environmental extended input-output analysis, supplemented by a partial equilibrium model reflecting changes of the agricultural sector to modified diets. It results that agricultural production does not decrease significantly in reaction to reduced food consumption, due to a changed trade balance and substitution effects.     

用吴方法计算Benjamin方程的势对称

本文中用微分形式的吴方法计算了Benjamin方程的古典对称和势对称,并利用该方程的对称对其进行了约化和求解了对应的部分不变解.求解确定方程组时吴方法起到了关键作用.     

新疆对外贸易和经济增长关系的实证研究

文章使用新疆1985--2006年的统计数据,利用协整理论和格兰杰（Gmnger）因果关系检验对新疆国内生产总值、出口和进口贸易之间的关系进行实证分析。研究结果表明,新疆的国内生产总值与新疆的出口、进口之间存在长期稳定的关系,新疆经济增长是拉动新疆出口和进口的Granger原因,新疆的进口是新疆经济增长的Granger原因,但新疆的出口却不是新疆经济增长的Granger成因。因此,应多方位加强出口产业与出口产品的工作,实现新疆对外贸易和新疆的经济增长良性互动发展。     

内蒙古经济增长与居民储蓄、投资关系动态分析——基于VAR模型的实证研究

我们利用1985-2007年的时间序列数据,基于宏观和动态的视角,对我国居民消费及其影响因素进行了实证分析。Johansen协整检验的结果说明我区经济增长与居民储蓄、投资关系之间存在一种长期均衡关系。向量自回归VAR模型的动态分析表明,我区经济增长对自身的冲击产生持续响应,经济增长呈现出一定程度的＂惯性＂特征;投资对GDP的冲击是正向的,居民储蓄对GDP的短期影响不明显,但长期为反向。通过分析揭示了投资是内蒙古近些年经济快速发展的主要动力。     

基于共生理论对政府购买服务的实践性反思——以湘川情社会工作服务中心为例

政府购买服务能提高第一部门的社会影响力和推动第三部门的发展,逐渐被政府、非政府组织和专家学者重视并得以施行。但湘川情社会工作服务中心在践行这一举措时,受偏利共生的影响使其独立性有所改变。因此,只有实现互惠共生才能不断完善政府购买服务,并将其逐渐推广。     

价格国际传递链中的“中国因素”研究 ──基于非线性Granger因果检验

 传统的Granger因果检验方法在现代经济学研究领域中得到了广泛的应用,然而,近年来的研究却发现,传统的Granger因果检验方法可能因忽略变量间的非线性关系而导致结论出现显著偏差。有鉴于此,本文首次采用最新发展的非线性Granger因果检验方法——Diks和Panchenko（2006）提出的非参检验方法,对中国在价格国际传递链中的地位与作用展开非线性研究。研究结果表明,通货膨胀在国际传递过程中呈现出显著的非线性动态变化趋势,而进一步的分析则发现在价格水平非线性传递中,作为世界第一大经济实体的美国发挥着主导作用,而中国对贸易伙伴国物价水平的冲击则十分微小,中国既无输出通货紧缩,也无输出通货膨胀,与此同时,本文还发现,现阶段中国物价水平呈现明显的外部“输入性”特征,因此,为了实现物价的长期稳定,我们必须在较好地应对国际冲击的同时,防范“输入型通货紧缩”与“输入型通货膨胀”的引发风险。