Guidelines for accurate EC50/IC50 estimation

This article provides minimum requirements for having confidence in the accuracy of EC50/IC50 estimates. Two definitions of EC50/IC50s are considered: relative and absolute. The relative EC50/IC50 is the parameter c in the 4-parameter logistic model and is the concentration corresponding to a response midway between the estimates of the lower and upper plateaus. The absolute EC50/IC50 is the response corresponding to the 50% control (the mean of the 0% and 100% assay controls). The guidelines first describe how to decide whether to use the relative EC50/IC50 or the absolute EC50/IC50. Assays for which there is no stable 100% control must use the relative EC50/IC50. Assays having a stable 100% control but for which there may be more than 5% error in the estimate of the 50% control mean should use the relative EC50/IC50. Assays that can be demonstrated to produce an accurate and stable 100% control and less than 5% error in the estimate of the 50% control mean may gain efficiency as well as accuracy by using the absolute EC50/IC50. Next, the guidelines provide rules for deciding when the EC50/IC50 estimates are reportable. The relative EC50/IC50 should only be used if there are at least two assay concentrations beyond the lower and upper bend points. The absolute EC50/IC50 should only be used if there are at least two assay concentrations whose predicted response is less than 50% and two whose predicted response is greater than 50%. A wide range of typical assay conditions are considered in the development of the guidelines.     

基于最小一乘准则的上证指数突变点研究

很多研究表明,上证指数序列既有结构突变的特征,也有厚尾的特征。但大部分现有的研究都没有考虑其厚尾特征对变点估计的影响。本文基于最小一乘准则提出了一个估计厚尾数据中变点的方法。模拟研究表明,当数据具有厚尾特征时,基于最小一乘准则的变点估计比基于最小二乘准则的估计有效。对上证指数的实证结果表明,基于最小一乘准则估计出的变点能更好地描述中国股票市场的结构突变特征。     

学术论文的选题技巧与独创性

学术论文选题需突出“下沉到点,点面兼顾”的原则。首先,切忌大而无当、浮泛不实。所选“点”应该是有新意的、关键性的和前景广阔的“点”;其次,学术论文选题要把“点”置于“面”的整体之中予以统筹考虑,尽量做到选题系列化和小中见大。此外,选择“点”,要考虑“点”所在“面”的“恰当性”,就是说,研究方向的选择切忌“变化快”、“难度大”和“自由度过低”等。学术论文的独创性要努力实现选题新、材料新、方法新和观点新。材料新即是文章中使用的是学界没有发现过或对于某一主题没有使用过的材料。方法新,包括创造新的方法、从其他领域引进新理论和新方法或采取观察问题的新角度等;观点新,除了较之前人的研究,在论文观点上应当有所前进外,还有一个创新程度和分量的问题,即要拒绝平庸、追求冲击力。      

Bent‐cable regression with autoregressive noise

Motivated by time series of atmospheric concentrations of certain pollutants the authors develop bent‐cable regression for autocorrelated errors. Bent‐cable regression extends the popular piecewise linear (broken‐stick) model, allowing for a smooth change region of any non‐negative width. Here the authors consider autoregressive noise added to a bent‐cable mean structure, with unknown regression and time series parameters. They develop asymptotic theory for conditional least‐squares estimation in a triangular array framework, wherein each segment of the bent cable contains an increasing number of observations while the autoregressive order remains constant as the sample size grows. They explore the theory in a simulation study, develop implementation details, apply the methodology to the motivating pollutant dataset, and provide a scientific interpretation of the bent‐cable change point not discussed previously. The Canadian Journal of Statistics 38: 386–407; 2010 © 2010 Statistical Society of Canada     

Time truncated acceptance sampling plans for generalized exponential distribution

Acceptance sampling plans for generalized exponential distribution when the lifetime experiment is truncated at a pre-determined time are provided in this article. The tables are provided for the minimum sample size required to ensure a certain median life of the experimental unit when the shape parameter is two. The operating characteristic function values of the sampling plans and the associated producer's risks are also presented. It is shown that the tables presented here can be used if instead of median life, other percentile life is chosen as the criterion or if the shape parameter is not two. Examples are provided for illustrative purposes.     

DELETE-2 AND DELETE-3 JACKKNIFE PROCEDURES FOR UNMASKING IN REGRESSION

Single-case deletion regression diagnostics have been used widely to discover unusual data points, but such approaches can fail in the presence of multiple unusual data points and as a result of masking. We propose a new approach to the use of single-case deletion diagnostics that involves applying these diagnostics to delete-2 and delete-3 jackknife replicates of the data, and considering the percentage of times among these replicates that points are flagged as unusual as an indicator of their influence. By considering replicates that exclude certain collections of points, subtle masking effects can be uncovered.     

自酿葡萄酒的卫生指标和理化指标的检测

本实验以手工酿造的葡萄酒为原料,分别用维生素C试验盒法、密度瓶法、甲醇比色法和大肠菌群9管发酵法来测定葡萄酒酿造过程中的酒精度、甲醇的含量,维生素C含量、菌落总数和大肠菌群情况.结果显示,自酿葡萄酒的酒精度达（8.24～8.28）%、甲醇含量为0.029g/100mL,符合国家新标准中规定的红葡萄酒甲醇含量.维生素C随着酿造时间的延长,含量逐渐下降,由20d的28.536μg/mL降低到90d的25.013μg/mL.菌落总数和大肠菌群均符合国家标准.     

参照依赖的消费者选择及其建模方法回顾与展望

参照依赖的消费者偏好和选择一直是营销学者的热点研究领域。学者们对如何在定量营销模型中考虑参照依赖的消费者偏好进行了诸多探索和方法创新,然而,目前却没有相关研究对这些建模方法进行较为系统的总结和梳理。为了填补这个研究空白,本研究回顾了消费者行为和决策领域中参照点的相关文献,并对参照依赖模型进行了系统的梳理。本文首先对参照点的定义和分类标准进行了综述和讨论。在此基础上,本文详细分析了现有实证研究中融入参照依赖的模型结构,并从模型使用的理论框架和参照属性的数量等几个方面对现有实证模型进行了分类和比较。最后,本文总结了现有相关研究的不足,并指出了该领域将来的研究方向。     

谈物流英语课程中的翻译教学

从当代物流企业对物流人才的能力要求入手,指出了专业外语知识及其应用能力是物流人才的必备素质,突出强调了高校教育中培养物流专业学生的翻译能力的重要性,并针对学生的实际翻译水平提出了五个翻译教学要点,旨在引导学生在翻译物流英语语句时学会从语法分析、专业范围、上下文逻辑关系、行文习惯和文体特征来分析和改进自己的翻译,同时还提出了三条教学方法,以此来帮助学生提高他们的专业英语翻译水平。     

关于服务业统计若干问题的探讨

 服务业已经成为我国国民经济重要的新增长点,但中国的服务业统计却处于严重滞后的状态,亟须探索服务业统计的理论和方法,藉以建立和完善服务业统计调查制度。本文分析了目前服务业统计的问题症结及其解决思路,并澄清了有关服务业与第三产业的基本概念和整体范围问题。