TESTS FOR EQUALITY OF TWO DISTRIBUTIONS WITH CORRELATED INTERVAL CENSORED LIFE-TIMES

ABSTRACT

Large sample properties of Life-Table estimator are discussed for interval censored bivariate survival data. We restrict our attention to the situation where response times within pairs are not distinguishable, and the univariate survival distribution is the same for any individual within any pair. The large sample properties are applied to test for equality of two distributions with correlated response times where treatments are applied to different independent sets of cohorts. Data, which can be separated into two independent sets, from an angioplasty study where more than one procedure is performed on some patients are used to illustrate this methodology.     

Fast Covariance Estimation for Innovations Computed from a Spatial Gibbs Point Process

In this paper, we derive an exact formula for the covariance of two innovations computed from a spatial Gibbs point process and suggest a fast method for estimating this covariance. We show how this methodology can be used to estimate the asymptotic covariance matrix of the maximum pseudo‐likelihood estimator of the parameters of a spatial Gibbs point process model. This allows us to construct asymptotic confidence intervals for the parameters. We illustrate the efficiency of our procedure in a simulation study for several classical parametric models. The procedure is implemented in the statistical software R , and it is included in spatstat , which is an R package for analyzing spatial point patterns.     

New Algorithms for Evaluating the Log-Likelihood Function Derivatives in the AI-REML Method

In this study, we propose several improvements of the Average Information Restricted Maximum Likelihood algorithms for estimating the variance components for genetic mapping of quantitative traits. The improved methods are applicable when two variance components are to be estimated. The improvements are related to the algebraic part of the methods and utilize the properties of the underlying matrix structures.

In contrast to previously developed algorithms, the explicit computation of a matrix inverse is replaced by the solution of a linear system of equations with multiple right-hand sides, based on a particular matrix decomposition. The computational costs of the proposed algorithms are analyzed and compared.     

Improved Likelihood Inference on Testing the Difference of Non Centrality Parameters of Two Independent Non central t Distributions with Identical Degrees of Freedom

Kim and Hayter (2008 Kim , J. , Hayter , A. J. ( 2008 ). Testing the equality of the non centrality parameters of the two non central t-distributions with identical degrees of freedom . Communications in Statistics: Simulation and Computation 37 : 1709 – 1717 .[Taylor & Francis Online], [Web of Science ®] , [Google Scholar]) showed that testing the difference of the non centralities of two non central t distributions, which have identical degrees of freedom, is the equivalent to testing the difference of two signal-to-noise ratios for two independent samples from different normal distributions. Moreover, from a biomedical research point of view, the above test is also equivalent to testing the existence of the effect size when the sample sizes of the control group and treatment group are the same. In this article, two third-order likelihood-based methods are proposed to approximate the p-value for this significance test problem. A real life example is used to illustrate that results from the proposed methods and the existing methods can be quite different. Simulation results show that the proposed methods give remarkable accuracy even when sample size reaches the smallest possible value.     

基于比较优势及规模经济的国际贸易万能公式探讨

为了探讨国际贸易发生的真正原因,定义了比较优势势力和规模经济势力的概念。运用对比方法和图形方法,通过放松一些假设条件来考察"两个版本"的规模经济引发国际贸易的过程,将比较优势和规模经济统一起来,发现了国际贸易"万能公式"。研究结论认为:比较优势和规模经济共同引发了国际贸易,在引入"补偿贸易条件线"概念条件下,可以将国际贸易的起因分解成比较优势势力效应和规模经济势力效应。同时,国际贸易"万能公式"可以用来解释里昂惕夫之谜。     

海南野生灵芝培养基配方优化

以琼州学院栽培灵芝培养基配方为基础,通过对海南尖峰岭的黄边灵芝(Ganoderma luteomarhi-natum)和咖啡网孢芝(Humphreya coffeatum)培养基配方进行优化,并对实验结果进行比较分析,得出一级种最优培养基为PDA+1/4MS(马铃薯:葡萄糖:琼脂:MS培养基为10∶1∶1∶0.25);二级种的最优培养基配方为Y1005(木屑78%、麦麸或米糠20%、蔗糖1%、石膏1%、含水50-60%);三级种的最优培养基为Y3102(木屑73%、黄豆粉5%、麦麸20%、蔗糖1%、石膏1%、含水60-65%).     

用线性代数方法研究二次曲线

用线性代数二次型的理论,以矩阵为工具,讨论了二次曲线的分类和退化为直线的充要条件,获得了新的充分必要条件和相应的直线方程公式。     

多相管流流体温度分布计算公式的推导与应用

以两相流动的能量守恒方程为依据,推导出了用于多相管流温降计算的一个通用公式,该公式考虑了焦耳汤姆逊效应导致的温降,液体摩擦生热引起的温升,以及地形起伏、气液相速度变化等因素对流体温度分布的影响,并用两个现场实例验证了四个常用温度计算简化公式在油气混输工艺计算中的有效性。与实测管线终点温度对比验算结果表明,影响混输管线温降的主要因素是传热系数、焦耳汤姆逊效应、液体摩擦生热,而气液相速度变化及地形起伏对温降计算影响较小,可以忽略不计。     

温度、时间和水分对配合饲料脂质酸败的影响

采用三因素二次回归正交组合设计 ,研究了温度 (6～ 4 2℃ )、时间 (3～ 57d)和水分 (9%～ 1 8% )与配合饲料 (1 0～ 2 0kg仔猪 )脂质酸败的关系。试验结果表明 :脂质水解酸败随着温度升高、时间延长和水分含量升高 ,呈极显著线性增强 (P <0 .0 1 )。水分范围 1 6%～ 1 8%配合饲料脂质氧化酸败最慢 ,随着饲料水分含量的降低 (低于 1 6% ) ,温度的升高 (6～ 4 2℃ )和时间的延长 (3～ 57d) ,脂质氧化酸败显著地增强 (P <0 .0 5)。水分含量 1 6% ,贮藏温度低于 2 0 .6℃ ,贮藏时间在 2 4 .0d内 ,饲料未产生酸败味