Adam Petrie  Thomas R. Willemain 《Statistical Analysis and Data Mining》2010,3(4):236-252

We introduce the ‘snake’, a new tool for the visualization and exploration of a multivariate dataset. The snake connects each data point along a single short path. Using techniques from the Traveling Salesman Problem (TSP), it is possible to find such a path in polynomial (nearly quadratic) computational time. A plot of the individual segment lengths versus their position along the path transforms the original multidimensional dataset into a one‐dimensional ‘time‐series’ of interpoint distances. The snake traces the local structure of a datacloud, so this visualization is most useful for detecting density fluctuations: regions of high density appear as many consecutive short segments, while regions of low density appear as many consecutive long segments. Dips in the time series reveal the presence of clustering and can be used to count the number of modes in the datacloud. We illustrate the technique on a variety of artificial and real‐world datasets. Copyright © 2010 Wiley Periodicals, Inc. Statistical Analysis and Data Mining 3: 236‐252, 2010  相似文献   

    

Thomas A. Louis 《Risk analysis》2010,30(3):346-348

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Larry E. Greiner  Thomas G. Cummings 《Global Business and Organizational Excellence》2011,30(3):50-56

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Thomas Lagoarde‐Segot 《Global Business and Organizational Excellence》2011,31(1):38-53

Although the main responsibility of firms may be to maximize their profits, organizations stand to gain much from the development of corporate social responsibility (CSR) strategies. This article reviews the connection between CSR and financial performance and discusses existing multilateral initiatives that global managers and investors are taking to align their business decisions with social and environmental needs. Moreover, an analysis of developments in six emerging markets—Malaysia, South Africa, Egypt, Turkey, Brazil, and Morocco—highlights how ongoing regulatory reforms provide incentives for company sustainability. The adoption of proactive CSR strategies while generating and disseminating robust and quantitative extra‐financial information to shareholders and regulators is an emerging driver of global competitiveness. Therefore, regulators and leaders of industrial organizations and business schools would do well to incorporate these elements into their twenty‐first‐century strategies. © 2011 Wiley Periodicals, Inc.  相似文献   

    

Adiel T. De Almeida Filho  Christophe Mues  Lyn C. Thomas 《Production and Operations Management》2010,19(6):698-708

This paper builds a dynamic programming model to optimize the collections process in consumer credit. It determines which collections actions should be undertaken and how long they should be performed, including theoretical results about the form of the optimal policy under certain conditions. Finally, a case study is described based on data from the collections department of a European bank.  相似文献   

    

Thorsten Dickhaus  Thomas Royen 《Statistics》2015,49(2):427-454

We are concerned with three different types of multivariate chi-square distributions. Their members play important roles as limiting distributions of vectors of test statistics in several applications of multiple hypotheses testing. We explain these applications and consider the computation of multiplicity-adjusted p-values under the respective global hypothesis. By means of numerical examples, we demonstrate how much gain in level exhaustion or, equivalently, power can be achieved with corresponding multivariate multiple tests compared with approaches which are only based on univariate marginal distributions and do not take the dependence structure among the test statistics into account. As a further contribution of independent value, we provide an overview of essentially all analytic formulas for computing multivariate chi-square probabilities of the considered types which are available up to present. These formulas were scattered in the previous literature and are presented here in a unified manner.  相似文献   

    

Petra Bůžková  Thomas Lumley 《统计学通讯:模拟与计算》2015,44(1):247-256

Cox regression is widely used to analyze discrete survival time data. Differential endpoint follow-up across sub-cohorts where distribution of a covariate varies may cause typical estimators to be biased or inefficient. We demonstrate that with Cardiovascular Health Study data for incident type 2 diabetes. Two cohorts with extremely different race distribution have differential follow-up for fasting glucose levels. We study various scenarios of Cox regression. We suggest an alternative approach, Poisson generalized estimating equations with an offset to accommodate the differential follow-up. We use simulations to contrast the methods.  相似文献   

    

Wai Yin Yeung  John Whitehead  Bruno Reigner  Ulrich Beyer  Cheikh Diack  Thomas Jaki 《Pharmaceutical statistics》2015,14(6):479-487

One of the main aims of early phase clinical trials is to identify a safe dose with an indication of therapeutic benefit to administer to subjects in further studies. Ideally therefore, dose‐limiting events (DLEs) and responses indicative of efficacy should be considered in the dose‐escalation procedure. Several methods have been suggested for incorporating both DLEs and efficacy responses in early phase dose‐escalation trials. In this paper, we describe and evaluate a Bayesian adaptive approach based on one binary response (occurrence of a DLE) and one continuous response (a measure of potential efficacy) per subject. A logistic regression and a linear log‐log relationship are used respectively to model the binary DLEs and the continuous efficacy responses. A gain function concerning both the DLEs and efficacy responses is used to determine the dose to administer to the next cohort of subjects. Stopping rules are proposed to enable efficient decision making. Simulation results shows that our approach performs better than taking account of DLE responses alone. To assess the robustness of the approach, scenarios where the efficacy responses of subjects are generated from an E _max model, but modelled by the linear log–log model are also considered. This evaluation shows that the simpler log–log model leads to robust recommendations even under this model showing that it is a useful approximation to the difficulty in estimating E _max model. Additionally, we find comparable performance to alternative approaches using efficacy and safety for dose‐finding. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

    

Lesa L. Aylward  Hong Cheng  Colleen Beall  Thomas B. Starr  Robert Brunet  Gaétan Carrier  Elizabeth Delzell 《Risk analysis》2007,27(1):9-10

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Thomas Knetsch  Ulrich Hauptmanns 《Risk analysis》2005,25(1):189-198

Stochastic effects and data uncertainties are present in any engineering calculation. Their impact may be particularly important if they concern the design of process equipment. A calculation model for the dynamic behavior of a heat exchanger and procedures to deal with the related uncertainties are presented. Their propagation through the calculation by means of a Monte Carlo approach is shown. The temperature at the heat exchanger outlet and the step response of a sudden variation in the heat exchanger inlet temperature are simulated and evaluated by way of example. It is demonstrated that the inclusion of stochastic effects and uncertainties provides a more reliable basis for design decisions and hence reduces the probability of errors.  相似文献