Two separate effects of variance heterogeneity on the validity and power of significance tests of location

Heterogeneity of variances of treatment groups influences the validity and power of significance tests of location in two distinct ways. First, if sample sizes are unequal, the Type I error rate and power are depressed if a larger variance is associated with a larger sample size, and elevated if a larger variance is associated with a smaller sample size. This well-established effect, which occurs in t and F tests, and to a lesser degree in nonparametric rank tests, results from unequal contributions of pooled estimates of error variance in the computation of test statistics. It is observed in samples from normal distributions, as well as non-normal distributions of various shapes. Second, transformation of scores from skewed distributions with unequal variances to ranks produces differences in the means of the ranks assigned to the respective groups, even if the means of the initial groups are equal, and a subsequent inflation of Type I error rates and power. This effect occurs for all sample sizes, equal and unequal. For the t test, the discrepancy diminishes, and for the Wilcoxon–Mann–Whitney test, it becomes larger, as sample size increases. The Welch separate-variance t test overcomes the first effect but not the second. Because of interaction of these separate effects, the validity and power of both parametric and nonparametric tests performed on samples of any size from unknown distributions with possibly unequal variances can be distorted in unpredictable ways.     

“消极自由”的个人联合体——论诺齐克的异质性“乌托邦”

文章阐述了诺齐克的消极自由主义国家观。作者认为诺齐克的乌托邦理论以“人是目的,而不仅仅以人为工具”的道德边际约束为根本原则、以要求“个人存在权”为“异质性乌托邦”的立论基础。这种“消极自由”的个人联合体向人们展示:自由的共同体不仅使所有的善同时并行,而且使历史上不同的生活样态同时存在。      

我国通货膨胀预期的微观基础研究

 通货膨胀预期的微观基础是一个重要的理论问题和实践问题,但是至今为止相关的研究还非常少。本文采用中国人民银行的《居民储蓄问卷调查系统》数据库,从经济主体的经济特征和人口统计特征两方面详细研究哪些因素会显著影响居民通胀预期。研究结果表明：人们对未来家庭经济状况的信心、风险厌恶程度和金融参与及熟悉度、家庭所处阶层、人们对现阶段经济运行状况的满意程度以及最近家庭所处的经济环境都是形成异质性通胀预期的重要原因。研究结果对于制定更加科学的货币政策和加强通胀预期管理具有重要的参考价值。     

贝叶斯隐马尔科夫异质面板模型及应用研究

针对不可观测异质性非时变假设导致的删失变量偏差及推断无效问题,构建贝叶斯隐马尔科夫异质面板模型,刻画截面个体间的动态时变不可观测异质性,诊断经济系统环境中可能存在的隐性变点,设计相应的马尔科夫链蒙特卡洛抽样算法估计模型参数,并对中国各地区的金融发展与城乡收入差距关系进行实证分析,捕捉到金融发展与城乡收入差距间长期稳定关系的隐性变化,发现了区域个体不可观测异质性存在的动态时变特征。研究结果表明各参数的迭代轨迹收敛且估计误差非常小,验证了贝叶斯隐马尔科夫异质面板模型的有效性。     

养老金制度变革的福利损益与再分配研究

本文借鉴Heckman和Raj分析框架,结合苏州工业园区金保工程管理数据,构建了养老金制度由完全积累制向部分积累制变革的反事实微观评估模型。鉴于参保职工异质性,本文采用分位数分析,用“替代率增幅分布”代替“平均替代率增幅”,评估制度变革的个体福利损益;又引入均值回归以及分位数回归,构建“替代率增幅”与“工资”等影响因素的经济结构模型,估计Raj充分信息评估指标,评估制度变革的收入再分配效应。本文在方法上整合了精算模型和经济结构模型,拓展了传统的反事实政策评估方法;在实务上为政府充分利用金保工程管理数据、辅助决策社会保障提供了一种范式。     

地方政府性债务影响经济增长路径的区域异质性分析

地方政府性债务影响经济增长的路径具有显著的区域异质性，这种异质性研究有利于加强地方政府性债务管理的有效性。公共投资、私人投资与公共支出是地方政府性债务影响经济增长的三条主要路径。文章在提出债务规模对三条路径影响都是非线性，且作用可能存在异质性假设的基础上，选取2010年到2016年，30个省（含自治区、直辖市）的相关数据，对全国、东、中、西部地区，影响经济增长的三条路径进行实证研究。东部地区的地方政府性债务规模增加，对公共投资无显著的影响，对私人投资有倒U型影响（拐点约为19%），对公共支出有显著的负面影响。中部地区的政府性债务规模增加对公共投资、私人投资的影响都是倒U型的（拐点分别约为30%和28%），对公共支出有显著的负面影响。西部地区的政府性债务规模增加对公共投资、私人投资和公共支出都存在倒U型影响（拐点均在70%以上）。     

Evaluate the relative efficiency of a targeted clinical trial design to an untargeted design under the issue of cost

In this article, we evaluate the relative cost of a targeted design to an untargeted design for a randomized clinical trial comparing a new treatment to a control. We observed that when the ratio of screen cost per person and drug cost per person is very small, say 0.008, the trial cost for conducting a targeted design might be fewer than that for conducting an untargeted design. When the difference between the treatment effect for the targeted patients and the treatment effect for the untargeted patients is increased, the savings in trial cost for the targeted design would be increased significantly. The greater sensitivity and specificity for the screen tool will lead to greater savings in trial cost for the targeted design. The relative cost of a targeted design to an untargeted design is associated with the treatment effect difference between targeted and untargeted patients, the proportion of targeted patients in the population, the screen tool performance, and the ratio of drug cost per person and screen cost per person.     

Power of the adjusted Q statistic to evaluate heterogeneity in meta-analyses of cluster randomized trials

Because of its simplicity, the Q statistic is frequently used to test the heterogeneity of the estimated intervention effect in meta-analyses of individually randomized trials. However, it is inappropriate to apply it directly to the meta-analyses of cluster randomized trials without taking clustering effects into account. We consider the properties of the adjusted Q statistic for testing heterogeneity in the meta-analyses of cluster randomized trials with binary outcomes. We also derive an analytic expression for the power of this statistic to detect heterogeneity in meta-analyses, which can be useful when planning a meta-analysis. A simulation study is used to assess the performance of the adjusted Q statistic, in terms of its Type I error rate and power. The simulation results are compared to that obtained from the proposed formula. It is found that the adjusted Q statistic has a Type I error rate close to the nominal level of 5%, as compared to the unadjusted Q statistic commonly used to test for heterogeneity in the meta-analyses of individually randomized trials with an inflated Type I error rate. Data from a meta-analysis of four cluster randomized trials are used to illustrate the procedures.