Combining estimates from multiple early studies to obtain estimates of response: using shrinkage estimates to obtain estimates of response

Development of anti-cancer therapies usually involve small to moderate size studies to provide initial estimates of response rates before initiating larger studies to better quantify response. These early trials often each contain a single tumor type, possibly using other stratification factors. Response rate for a given tumor type is routinely reported as the percentage of patients meeting a clinical criteria (e.g. tumor shrinkage), without any regard to response in the other studies. These estimates (called maximum likelihood estimates or MLEs) on average approximate the true value, but have variances that are usually large, especially for small to moderate size studies. The approach presented here is offered as a way to improve overall estimation of response rates when several small trials are considered by reducing the total uncertainty.The shrinkage estimators considered here (James-Stein/empirical Bayes and hierarchical Bayes) are alternatives that use information from all studies to provide potentially better estimates for each study. While these estimates introduce a small bias, they have a considerably smaller variance, and thus tend to be better in terms of total mean squared error. These procedures provide a better view of drug performance in that group of tumor types as a whole, as opposed to estimating each response rate individually without consideration of the others. In technical terms, the vector of estimated response rates is nearer the vector of true values, on average, than the vector of the usual unbiased MLEs applied to such trials.     

Bayesian dynamic models for survival data with a cure fraction

In this paper, we propose a new class of semi-parametric cure rate models. Specifically, we construct dynamic models for piecewise hazard functions over a finite partition of the time axis. Allowing the size of partition and the levels of baseline hazard to be random, our proposed models provide a great flexibility in controlling the degree of parametricity in the right tail of the survival distribution and the amount of correlations among the log-baseline hazard levels. Several properties of the proposed models are derived, and propriety of the implied posteriors with improper noninformative priors for regression coefficients based on the proposed models is established for the fixed partition of the time axis. In addition, an efficient reversible jump computational algorithm is developed for carrying out posterior computation. A real data set from a melanoma clinical trial is analyzed in detail to further demonstrate the proposed methodology.     

利率政策对股市个人投资者行为影响的实证检验

以中国部分基本利率调整为研究对象,采用事件研究分析法,对相关时间段内的股市个人投资者交易频率和交易额度的累积差异情况进行了计算。结果显示利率变动前后投资者的交易频率和交易额度均有显著变化,但变化时期短,从而验证了利率政策对个体投资者行为有显著影响,同时表明了投资者行为存在非理性特征,揭示出中国证券市场存在非有效性,为中国宏观货币政策的调整提供借鉴。     

基于技术变革分类的技术追赶过程研究

本文基于技术变革分类,提出渐进型、破坏型、革命型三种技术追赶路径,并提炼各路径不同发展阶段的创新重点及动态演化特征。借助曲线拟合方法,初步获得三种技术追赶路径的创新演化特征。在渐进型技术追赶过程中,创新率的最大值出现在路径后期,之后虽有下降,但幅度不大;在破坏型技术追赶过程中,尽管创新率曲线呈线性特征,但从散点图特征来看,仍然存在先高、后低、再升高的趋势;在革命型技术追赶过程中,创新率迅速提高至峰值后,迅速下降。     

Complete consistency for the estimator of nonparametric regression model based on martingale difference errors

Abstract

In this paper, we study the complete consistency for the estimator of nonparametric regression model based on martingale difference errors, and obtain the convergence rates of the complete consistency by using the inequalities for martingale difference sequence. Finally, some simulations are illustrated.     

基于部分延迟支付期限的易损品经济批量订货模型研究

已有考虑延期付款的EOQ订货模型多为单层延期支付,而忽略了供应商与其上级供应商,或零售商与其下级零售商的关系。而实际易损品,由于资金约束导致零售商和下游顾客都延迟支付,不同层级延迟支付期限对运营成本与订货周期的策略影响如何?为此,文章在Huang’s模型基础上,考虑零售商、顾客都存在部分延期支付情况下,易损商品三阶段经济批量订货策略,证明了最优订货策略的存在性及唯一性,并分析了参数的影响特征。研究结果表明:(1)当零售商的延迟支付期限大于顾客的延迟支付期限时,零售商最优订货周期和最优订货数量随着变质率的增大而减小,此时零售商应该选择增加订货频率,减少订货数量的策略。(2)当零售商的延迟支付期限小于顾客延迟支付期限时,零售商的最优订货周期和最有订货数量随着变质率的增大而增大,此时零售商应该选择减少订货频率,增加每次订货的订货数量策略。     

宫内节育器使用效果的调查分析

对2659例已婚育龄妇女放置宫内节育器(IUD)后1年进行了调查,了解IUD的使用效果。结果显示,农村妇女IUD放置后1年使用率为84.2%,低于城市妇女(P<0.001);带器妊娠和IUD脱落是IUD停止使用的主要原因。应加强技术服务,提高IUD的续用率。     

新疆人口出生率的差异及其变动特征解析

新疆维吾尔自治区由于特殊的地理位置造成地区间、城乡间经济发展水平参差不齐,复杂的民族成分也使得各民族间的生育观念反差很大,这必然导致地区间、城乡间、民族间、季节间的出生率存在差异。本文汇总了新疆历年来人口出生率的数据,详细分析了出生率的变动特征和不同民族、城乡、地区、季节间出生率的历史变动规律。     

台湾-大陆人口老龄化比较研究

本文评述了台湾-大陆人口老龄化的历史发展过程及人口老龄化的特征;运用台湾-大陆的统计资料建立计量模型,从而运用定量的方式分析对比了两岸的人口老龄化成因;最终提出了关于缓解两岸人口老龄化冲击的措施。本研究不仅有助于增进两岸的了解,也为两岸互相汲取经验、互惠互利提供了帮助。     

中国人口劳动参与率与未来劳动力供给分析

对未来劳动力供给进行准确预测判断将有利于我们未来就业政策、现实人口政策和社会保障政策的科学制定,也是对未来人口与经济形势准确判定的依据,是一项非常重要的工作。在充分考虑人口老龄化、劳动参与率年龄模式变动以及受教育水平提高影响的基础上,对未来劳动供给进行预测。预测结果显示,如果不考虑65岁及以上人口的就业,到2016年将达到从业人员的高峰7.58亿,其后持续减少,到2050年前后减少到6.4亿;如果考虑65岁及以上人口的就业,我国的就业高峰将出现在2022年前后,到2045年以后,劳动力供给将大规模减少。届时劳动供养人口将会大大增加,这必须引起当代人在规划人口发展时的重视。