Exact sample size determination in a weibull test plan when there is time censoring

Engineers who conduct reliability tests need to choose the sample size when designing a test plan. The model parameters and quantiles are the typical quantities of interest. The large-sample procedure relies on the property that the distribution of the t -like quantities is close to the standard normal in large samples. In this paper, we use a new procedure based on both simulation and asymptotic theory to determine the sample size for a test plan. Unlike the complete data case, the t -like quantities are not pivotal quantities in general when data are time censored. However we show that the distribution of the t -like quantities only depend on the expected proportion failing and obtain the distributions by simulation for both complete and time censoring case when data follow Weibull distribution. We find that the large-sample procedure usually underestimates the sample size even when it is said to be 200 or more. The sample size given by the proposed procedure insures the requested nominal accuracy and confidence of the estimation when the test plan results in complete or time censored data. Some useful figures displaying the required sample size for the new procedure are also presented.     

论水平扭剪应力场对大裂缝系统的控制

本文根据地质力学和岩体结构力学原理，探讨水平扭剪应力场在大裂缝系统形成、转化和分布中的重要控制作用及其物理模型．文中认为，大裂缝系统是较大的直压型裂缝网络与扭剪型裂缝网络叠加的产物，主要分布在较强的水平扭剪应力和术平直压应力复合作用的区块；水平扭剪应力场是改造和控制大裂缝网络结构异向性的最重要因素。这为研究和勘探较大的隐伏裂缝系统，提供了新的成藏模式和理论依据。     

威布尔分布场合步加试验和步降试验的效率比较分析

 本文通过大量的Monte-Carlo模拟，在四个不同的准则下就威布尔分布比较了步进应力加速寿命试验和步降应力加速寿命试验的效率，认为步降应力加速寿命试验很值得推广，尤其是针对耗损型产品。     

Discrete Linnik Weibull distribution

Abstract

We introduce a new family of distributions using truncated discrete Linnik distribution. This family is a rich family of distributions which includes many important families of distributions such as Marshall–Olkin family of distributions, family of distributions generated through truncated negative binomial distribution, family of distributions generated through truncated discrete Mittag–Leffler distribution etc. Some properties of the new family of distributions are derived. A particular case of the family, a five parameter generalization of Weibull distribution, namely discrete Linnik Weibull distribution is given special attention. This distribution is a generalization of many distributions, such as extended exponentiated Weibull, exponentiated Weibull, Weibull truncated negative binomial, generalized exponential truncated negative binomial, Marshall-Olkin extended Weibull, Marshall–Olkin generalized exponential, exponential truncated negative binomial, Marshall–Olkin exponential and generalized exponential. The shape properties, moments, median, distribution of order statistics, stochastic ordering and stress–strength properties of the new generalized Weibull distribution are derived. The unknown parameters of the distribution are estimated using maximum likelihood method. The discrete Linnik Weibull distribution is fitted to a survival time data set and it is shown that the distribution is more appropriate than other competitive models.     

异质性视角下中国农村居民减贫效应研究——基于FGT贫困指数的分解新方法

在我国即将完成脱贫攻坚背景下,异质性在居民减贫并防返贫进程中逐渐起到关键作用。本文通过反事实分析法将收入分布变迁分解为均值、方差以及残差三种变化,进而将其引入贫困分解中,对我国农村及区域贫困进行分解。研究表明,引入收入分布变迁贫困分解结果具有稳健性,且农村居民收入增长效应与离散效应存在非对称性,提高收入已不足以弥补收入差距扩大带来的贫困加深效应,而异质效应和离散效应间存在对称性,居民异质性在减贫进程中逐渐起到关键作用。同时从区域视角看,东部区域异质效应减贫效果明显高于增长效应;中部区域增长效应和异质效应均具有显著减贫效果;而西南区域增长效应的减贫效果最显著。     

样本选择参数分位回归模型及其在工资分布分解中的应用

在工资差距分解问题中,研究者经常会遇到样本选择偏差问题,直接忽略会导致最终估计结果产生严重偏差,同时在众多工资差距分解方法中,相比于均值分解,分布分解方法更受研究者青睐。针对参数分位回归,本文首次提出可加形式与非可加形式的样本选择参数分位回归（SSPQR）模型,并基于这两类样本选择参数分位回归模型给出修正样本选择偏差后的参数分位回归工资差距分布分解方法。运用上述方法及已有的工资分布分解方法,借助CHNS2015年度城镇数据,本文研究了我国城镇男女工资差距及差距分解问题,得出以下结论：①男女工资差距主要来源是性别歧视问题;②经过样本选择偏差修正后,实际的工资差距更大,歧视问题更严重;③男女工资差距程度在不同分位点上结果不同,换句话说,我们不能简单地仅从平均水平来判断工资差距程度;④与其他已有方法计算结果比较发现,SSPQR计算的工资差距程度更大。     

Exact permutation inference for two sample repeated measures data

Experiments in which very few units are measured many times sometimes present particular difficulties. Interest often centers on simple location shifts between two treatment groups, but appropriate modeling of the error distribution can be challenging. For example, normality may be difficult to verify, or a single transformation stabilizing variance or improving normality for all units and all measurements may not exist. We propose an analysis of two sample repeated measures data based on the permutation distribution of units. This provides a distribution free alternative to standard analyses. The analysis includes testing, estimation and confidence intervals. By assuming a certain structure in the location shift model, the dimension of the problem is reduced by analyzing linear combinations of the marginal statistics. Recently proposed algorithms for computation of two sample permutation distributions, require only a few seconds for experiments having as many as 100 units and any number of repeated measures. The test has high asymptotic efficiency and good power with respect to tests based on the normal distribution. Since the computational burden is minimal, approximation of the permutation distribution is unnecessary.     

中国城乡收入分布动态演进及经验检验

 本文利用“中国营养和健康调查”家庭平均收入的模块数据，采用核密度估计、累积分布函数、洛伦茨曲线等方法刻画我国城乡居民收入分布的动态演进，结果表明，大多数家庭都分享了我国经济快速增长带来的成果，其中高收入阶层比低收入阶层更多地分享了经济成果，城市居民比农村居民更多地分享了经济成果。进一步地，非参数假设检验和相对偏差估计结果表明，N. C. Kakwani的三参数函数和简易公式的基尼系数估计精度较高，广义Logistic分布函数是估计城乡居民收入分布的可行选择。     

Distribution of linear combination of exponential variates

The exact distribution of a linear combination of n independent negative exponential random variables, when the coefficients of the linear combination are distinct and positive quantities, is well-known. This paper extends the above result to the general case, namely when the coefficients are arbitrary real numbers, positive or negative, distinct or coincident.     

中美俄博弈模式分析:决策层级、动机及过程

以中美俄博弈的决策模式为研究对象,并通过列举中美和中俄两个具有合作性质的博弈案例,进而深入分析中美俄博弈的决策角色、决策动机和决策过程,指出决策角色可分为第一层级、第二层级和辅助层级,而国家利益是最重要的决策动机.为了追求决策效率,三国决策者紧密控制决策过程,防止其他权力部门分享决策权.