Evaluating the power of Minitab's data subsetting lack of fit test in multiple linear regression

Minitab's data subsetting lack of fit test (denoted XLOF) is a combination of Burn and Ryan's test and Utts' test for testing lack of fit in linear regression models. As an alternative to the classical or pure error lack of fit test, it does not require replicates of predictor variables. However, due to the uncertainty about its performance, XLOF still remains unfamiliar to regression users while the well-known classical lack of fit test is not applicable to regression data without replicates. So far this procedure has not been mentioned in any textbooks and has not been included in any other software packages. This study assesses the performance of XLOF in detecting lack of fit in linear regressions without replicates by comparing the power with the classic test. The power of XLOF is simulated using Minitab macros for variables with several forms of curvature. These comparisons lead to pragmatic suggestions on the use of XLOF. The performance of XLOF was shown to be superior to the classical test based on the results. It should be noted that the replicates required for the classical test made itself unavailable for most of the regression data while XLOF can still be as powerful as the classic test even without replicates.     

PROBLEMS WITH BINOMIAL TWO-SIDED TESTS AND THE ASSOCIATED CONFIDENCE INTERVALS

Confidence intervals for parameters of distributions with discrete sample spaces will be less conservative (i.e. have smaller coverage probabilities that are closer to the nominal level) when defined by inverting a test that does not require equal probability in each tail. However, the P‐value obtained from such tests can exhibit undesirable properties, which in turn result in undesirable properties in the associated confidence intervals. We illustrate these difficulties using P‐values for binomial proportions and the difference between binomial proportions.     

农业生产与经济增长关系的均衡分析

为探讨我国农业生产与经济增长之间的关系,选取1978-2006年我国历年农业产值和国内生产总值序列进行协整检验,结果表明我国农业生产与经济增长之间存在着长期稳定的动态均衡关系,农业产值每增加1%,将促进经济增长2.12%;误差修正模型表明,农业生产的短期变化对经济增长有显著的正效应,如果本期的经济增长偏离长期均衡值,那么到下一时期这一偏离度将有8%得以纠正;Granger因果关系检验表明,农业生产对经济增长具有短期效应,经济增长对农业生产具有长期促进作用;脉冲响应函数分析和方差分解的结果进一步表明,农业生产对经济增长的贡献较显著。     

BSE Risk Assessment as a Basis for Updating French Screening Policy

The current French bovine spongiform encephalopathy (BSE) surveillance system, based on rapid testing of all cattle over 24 months of age and on clinical diagnosis, detects all clinical cases and some preclinical cases of BSE. Several indicators point to a marked shrinkage of the French BSE epidemic in recent years, owing to risk reduction measures. Meat and bone meal, the only known vector of the BSE agent, was banned in feed for all farmed species in November 2000. Thus the surveillance system may be relaxed. The objective of this risk assessment study was to provide information for decisionmakers on the minimum age at which healthy and high-risk cattle now need to be screened with rapid tests. For this purpose, we used the back-calculation method to project the course of the BSE epidemic. We examined the predicted patterns of the number and age distribution of cases of BSE that would be detected by the different existing surveillance streams. Various theoretical sensitivities of rapid tests were explored. Assuming that feed-borne sources of infection no longer exist, and that BSE does not occur spontaneously, our models suggest that it would have been possible to raise the minimum age for rapid tests to 66 months in early 2006, whereas theoretical reasoning, based on the assumption that the total meat and bone meal ban was effective in November 2001, suggests that this age cutoff could only be raised to 48 months in early 2006. These results only apply to cattle born and bred in France. If the situation remains unchanged, the age cutoff could be raised incrementally each year.     

在教学中提高A、B级英语考试水平

近几年来,高职高专的英语应用能力考试得到了大大的推广,当下进行的高职教育评估对该项考试的过级率更是提出了更高的要求。对高职高专的英语应用能力A、B级考试做的相关教学探索,实践证明相关的作法实施得到了良好的效果。     

一株新的产毒性大肠杆菌的毒素检测

本文用两种方法同时检测一株大肠杆菌不耐热肠毒素,结果表明,免疫溶血法为阳性,改良 ELeK 试验为阳性,提示免疫溶血法灵敏度较高。     

对大学英语一份试卷的分析

IntroductionThis analysis first presents the relevant infor-mation about the test paper that the author used inChina in 2003.Then it evaluates the test in the as-pects of content validity,construct validity and re-liability in scoring.For those deficiencies exhibitedby the test,some suggestions are provided on howto improve the test in order to achieve validity,re-liability and practicality.Background informationThe test purpose.This was an achievement testfirmly based on the syllabus and th…     

批判视角下大学英语期末测试的问题与对策

地方本科院校大学英语期末测试主要存在以下问题:教育主管部门的行政干预;大学英语四级考试的消极影响;相关教师责任心不够强,测试理论水平、实践水平相对低下。批判语言测试主张从广阔的社会视域解决这些问题:敦促期末测试各利益相关方协同努力;实现语言测试专业化;体现以学习者为中心的理念;把对学习者的评价贯穿于英语学习的每一个环节。     

债券流动性与违约风险相关性溢价及实证研究

债券的流动性与违约风险都是影响债券溢价的重要因素,然而以往在违约风险最为突出的公司债券定价中却很少考虑两种风险相关性关系的影响,这与发达市场实证经验不符.在已有研究的基础上同时引入两种风险相关性,通过对Copula函数刻画的不同相关性结构情况下公司债券的收益率和风险变化分析,以及对中国短、中、长期公司债券市场数据的实证检验均发现,流动性与违约风险的相关性之间存在显著的正相关性,且对债券利差具有显著的影响和交互作用.     

原油价格变动对中国基础工业收益的影响——基于格兰杰因果关系检验的实证研究

以2006年1月4日-2014年7月31日的日数据为样本,采用向量自回归模型(VAR模型)、非线性检验、线性格兰杰因果关系检验、非线性格兰杰因果关系检验,选取电力及公用事业、钢铁、机械、基础化工、煤炭、原油石化六大基础工业,从行业角度研究原油价格对中国经济的影响关系。实证结果表明:原油价格变化率与钢铁、煤炭、石油石化行业存在显著的双向线性格兰杰因果关系,机械、基础化工到原油价格变化率存在显著的单向线性格兰杰因果关系,电力及公共事业与原油价格不存在线性格兰杰因果关系;原油价格变化率与6个基础工业存在显著地双向非线性因果关系。