Confidence intervals for the ratio of two variances

In this paper we consider confidence intervals for the ratio of two population variances. We propose a confidence interval for the ratio of two variances based on the t-statistic by deriving its Edgeworth expansion and considering Hall's and Johnson's transformations. Then, we consider the coverage accuracy of suggested intervals and intervals based on the F-statistic for some distributions.     

NFL Draftnikology: Euclidean Metrics and Other Approaches to Scoring Ranking Predictions

With viewership of NFL (National Football League) football in the US rising above 20 million, interest in the NFL Draft has also been at all-time highs in recent years. Much of this interest is directed toward the “NFL draftniks” who provide draft predictions—so-called “mock drafts”—leading up to the NFL Draft. Despite increasing interest in “NFL draftnikology,” the scoring methodology used to evaluate mock NFL drafts lags far behind. This study offers a few alternative approaches, including a Euclidean metrics approach to evaluating mock NFL drafts. The usefulness of our methodologies extends to evaluation of economic and financial analysts.     

基于JIT装配模式的网上超市订单分拣优化模型

订单分拣是大型网上超市生存和发展的关键环节，如何在数百万种商品中将订单要求的商品高效、准确地进行拣选并包装，是亟待解决的难题。本文以提高大型网上超市订单分拣方法的科学性为目标，针对订单拣选、集货复核、包装这一作业流程，基于JIT装配流水线思想，建立大型网上超市订单成组分拣的优化模型与求解方法。在构建订单分拣流程中各工序作业时间计算模型的基础上，建立了订单分批与排序的联合优化模型。围绕缩减求解空间的思想提出两阶段启发式优化方法。通过应用实例分析和灵敏度分析证明了算法的有效性。结果表明，本文提出的网上超市订单成组分拣方法相较于传统方法可较大幅度提高订单分拣的效率，为网上零售企业的订单拣选和包装作业流程的优化提供了理论指导。     

Nonparametric predictive inference for diagnostic test thresholds

Abstract

Measuring the accuracy of diagnostic tests is crucial in many application areas including medicine, machine learning and credit scoring. The receiver operating characteristic (ROC) curve and surface are useful tools to assess the ability of diagnostic tests to discriminate between ordered classes or groups. To define these diagnostic tests, selecting the optimal thresholds that maximize the accuracy of these tests is required. One procedure that is commonly used to find the optimal thresholds is by maximizing what is known as Youden’s index. This article presents nonparametric predictive inference (NPI) for selecting the optimal thresholds of a diagnostic test. NPI is a frequentist statistical method that is explicitly aimed at using few modeling assumptions, enabled through the use of lower and upper probabilities to quantify uncertainty. Based on multiple future observations, the NPI approach is presented for selecting the optimal thresholds for two-group and three-group scenarios. In addition, a pairwise approach has also been presented for the three-group scenario. The article ends with an example to illustrate the proposed methods and a simulation study of the predictive performance of the proposed methods along with some classical methods such as Youden index. The NPI-based methods show some interesting results that overcome some of the issues concerning the predictive performance of Youden’s index.     

现代篮球裁判员水平与篮球运动发展的辩证关系

运用文献资料调研和逻辑分析等研究方法,对篮球裁判在篮球运动发展中的作用进行了阐述和分析,探讨篮球裁判员在篮球运动发展中起到的关键性作用。在此基础上,提出篮球裁判员临场执法的原则和相关建议,旨在为篮球竞赛顺利进行和充分提高裁判员水平提供参考。     

Efficient computation of the distribution functions of student's t chi-squared and fto moderate accuracy

Ling (1978) recently reported on the accuracy of some approximations to the tail areas of F, chi-squared and F to help design efficient and moderately (3 to 5 decimal places) accurate programs for these probabilities. This paper examines two further approximations, and stresses the need for careful coding if one is to avoid loss of accuracy in single precision implementations on short word length computers. With careful coding five decimal places can easily be obtained for t and chi-squared probabilities, while for t four places are obtainable with reasonable computational effort.     

An Evaluation of Population Estimates in Florida: April 1, 2000

The housing unit (HU) method is the most commonly used method for making small-area population estimates in the United States. These estimates are used for a wide variety of budgeting, planning, and analytical purposes. Given their importance, periodic evaluations of their accuracy are essential. In this article, we evaluate the accuracy of a set of HU population estimates for counties and subcounty areas in Florida, as of April 1, 2000. We investigate the influence of differences in population size and growth rate on estimation errors; compare the accuracy of several alternative techniques for estimating each of the major components of the HU method; compare the accuracy of 2000 estimates with that of estimates produced in 1980 and 1990; compare the accuracy of HU population estimates with that of estimates derived from other estimation methods; consider the role of professional judgment and the use of averaging in the construction of population estimates; and explore the impact of controlling one set of estimates to another. Our results confirm a number of findings that have been reported before and provide empirical evidence on several issues that have received little attention in the literature. We conclude with several observations regarding future directions in population estimation research.     

雅典公民大会召开次数辨析

公民大会是雅典民主政治的最高权利机构,因此深入研究公民大会可以更好的加深我们对于雅典民主制度的认识。公民大会召开次数在雅典民主发展进程中并不是固定不变的,而是随着形势的发展变化而不断改变。     

热传导方程的高精度三次样条差分格式

基于一种三次样条四阶差分公式 ,提出了一种数值求解非齐次热传导方程的两层三结点高精度差分格式 .通过数值算例验证了格式的优良性态 .     

MD&A纵向文本相似度与分析师盈余预测准确性

注册制下,信息的真实、准确、完整是投资者合理判断证券价值的关键,分析师在信息作用于股价这一过程中扮演着重要的信息中介角色,而年报所披露的信息对分析师盈余预测至关重要。以2012—2021年沪深A股上市公司为样本,探究了管理层讨论与分析(MD&A)纵向文本相似度对分析师盈余预测准确性的影响。研究发现,MD&A纵向文本相似度越高,分析师盈余预测准确性越低,证实了“增量信息”假说。异质性分析表明,这种影响显著存在于规模小、高科技行业、媒体关注度低的公司中,并且公司位于市场化程度低省份时受此影响更大。进一步研究发现,MD&A纵向文本相似度越高,分析师盈余预测的正向偏差越大。此外,分析师盈余预测准确性的下降会进一步降低资本市场的信息效率。因此,上市公司应重视文本信息披露,避免披露内容样板化;分析师和监管部门应加强对上市公司文本信息披露的监督,优化资本市场信息环境。