Testing the rate ratio under inverse sampling based on gradient statistic

Inverse sampling is widely applied in studies with dichotomous outcomes, especially when the subjects arrive sequentially or the response of interest is difficult to obtain. In this paper, we investigate the rate ratio test problem under inverse sampling based on gradient statistic with the asymptotic method and parametric bootstrap technique. The gradient statistic has many advantages, for example, it is simple to calculate and competitive with Wald-type, score and likelihood ratio tests in terms of local power. Numerical studies are carried out to evaluate the performance of our gradient test and the existing tests, namely Wald-type, score and likelihood ratio tests. The simulation results suggest that the gradient test based on the parametric bootstrap method has excellent type I error control and large powers even in small sample design. Two real examples, from a heart disease study and a drug comparison study, are applied to illustrate our methods.     

涩北二号疏松砂岩气田出水规律研究

涩北二号气田是柴达木盆地的大型生物气田，岩性疏松，气层多而薄，存在边水，气水关系复杂。气田开发过程中气井出水普遍，出水量差异较大，产量递减较快，因此，认清气田出水规律是确保气田控水稳产的基础。以生产动态数据为基础，研究了气田各层组产水特征及水气比上升规律；通过气井出水水源的多因素合理识别，将气田出水井归结为4 种类型；并通过边水水侵量及水侵速度的计算，明确了气田不同层组边水水侵类型，认识了不同层组不同方向上的水侵速度不同；最后，通过地层累计含水率分布的计算，有效地确定了不同层组水侵前缘位置，为下一步气田控水、气井产量合理调整及气藏稳产奠定了基础。     

基于解释结构模型的企业汇率风险应急机制构建研究

由于中国大多数企业缺少对汇率风险的管理,加之汇率波动幅度及波动频率的不确定性增加,使暴露于汇率风险中的企业数量和风险头寸增加.因此,建立科学合理的企业汇率风险应急机制具有现实意义.文章运用解释结构模型(ISM)对构建企业汇率风险应急机制及其影响因素进行了分析研究.通过构建模型,明确了建立企业汇率风险应急机制将受5个等级的16个因素影响,其中2个因素为直接影响因素,5个因素为基础性影响因素.文章试图为企业汇率风险应急机制构建提供理论依据,为企业汇率风险应急管理实践提供有效路径.     

两种目标制下的我国最优货币政策研究

文章构造了一个开放经济下的混合型AD‐AS模型,并根据我国2003～2013年的统计数据对其进行了估计,分别求出了在通货膨胀目标制和利率平滑目标制下事先承诺型的最优货币政策规则。在没有扰动的情况下,我国的宏观经济系统在这两种最优货币政策下都是渐近稳定的。通过两种目标制下最优货币政策的比较,发现在控制产出缺口方面,通货膨胀目标制更有效,在利率的操作性方面,利率平滑目标制更合理。     

LPM模型下的利率政策及其作用

本文探讨在不完全信息条件下,央行以短期流动性效益目标,利用利率政策工具在银行间拆借市场、货币市场以及资本市场上的非对称性传导表现为基础,并以此为逻辑线索线进行分析,指出利率主义的深化、利率政策内生性需求下,利率政策效应在银行间拆借市场、货币市场与资本市场中的链接,因不同的产品时间反应不一致从而使得利率政策在不同的市场产生不同的有效性、内生性变化效果,继而阐明了有限参与市场条件下利率传导的非对称性有效性效应,说明国民经济发展中利率政策调控需要考虑定向调控利率的问题.对央行的定向调控等利率政策的制定与调整提出了合理化建议.     

基于高频面板数据的人民币汇率波动规律研究

基于2006—2013年的1771个人民币汇率日值高频数据,采用 GARCH 模型对人民币与美元、港币、日元、欧元及英镑之间的汇率波动规律进行实证分析。结果显示：（1）人民币兑五大外汇币种汇率的波动存在 ARCH 效应,其收益表现出明显的群聚特征;（2）人民币兑五大外汇币种汇率的波动均具有一定的记忆性,但除港币和日元外,大都会随时间缓慢衰减;（3）人民币兑五大外汇币种汇率的波动存在明显的杠杆效应,但不同币种对人民币升值的反应存在一定的差异。     

Stochastic comparisons of sample spacings in single- and multiple-outlier exponential models

This article studies some ordering results for the sample spacings arising from the single- and multiple-outlier exponential models. In the single-outlier exponential models, it is shown that the weak majorization order between the two hazard rate vectors implies the hazard rate order as well as the dispersive order between the corresponding sample spacings. We also extend this result from the single-outlier model to the multiple-outlier model for the special case of the second sample spacing. Furthermore, we obtain some necessary and sufficient conditions such that, on the one hand, the hazard rate, dispersive and usual stochastic orders, and on the other hand, the likelihood ratio and reversed hazard rate orders of the second sample spacings from two independent heterogeneous exponential random variables are equivalent.     

Variables acceptance reliability sampling plan for repairable items

Traditionally, acceptance reliability sampling plans have been developed for non-repairable items. However, the functions required for items become more and more complex and, accordingly, the items are composed of several components and tend to be repairable. In this paper, we consider variables acceptance reliability sampling plan for repairable items. We develop a variables acceptance sampling plan based on the failure and repair data observed during the testing period. It is shown that the developed sampling plan improves the reliability characteristic of the population and that the lifetimes of items before and after the reliability sampling test are stochastically ordered.     

Tests for Coefficients in High‐dimensional Additive Hazard Models

We consider hypothesis testing problems for low‐dimensional coefficients in a high dimensional additive hazard model. A variance reduced partial profiling estimator (VRPPE) is proposed and its asymptotic normality is established, which enables us to test the significance of each single coefficient when the data dimension is much larger than the sample size. Based on the p‐values obtained from the proposed test statistics, we then apply a multiple testing procedure to identify significant coefficients and show that the false discovery rate can be controlled at the desired level. The proposed method is also extended to testing a low‐dimensional sub‐vector of coefficients. The finite sample performance of the proposed testing procedure is evaluated by simulation studies. We also apply it to two real data sets, with one focusing on testing low‐dimensional coefficients and the other focusing on identifying significant coefficients through the proposed multiple testing procedure.     

Efficient Estimation of the Partly Linear Additive Hazards Model with Current Status Data

This paper focuses on efficient estimation, optimal rates of convergence and effective algorithms in the partly linear additive hazards regression model with current status data. We use polynomial splines to estimate both cumulative baseline hazard function with monotonicity constraint and nonparametric regression functions with no such constraint. We propose a simultaneous sieve maximum likelihood estimation for regression parameters and nuisance parameters and show that the resultant estimator of regression parameter vector is asymptotically normal and achieves the semiparametric information bound. In addition, we show that rates of convergence for the estimators of nonparametric functions are optimal. We implement the proposed estimation through a backfitting algorithm on generalized linear models. We conduct simulation studies to examine the finite‐sample performance of the proposed estimation method and present an analysis of renal function recovery data for illustration.