Calculation of the Prokhorov distance by optimal quantization and maximum flow

Calculating exact values of the Prokhorov metric for the set of probability distributions on a metric space is a challenging problem. In this paper probability distributions are approximated by finite-support distributions through optimal or quasi-optimal quantization, in such a way that exact calculation of the Prokhorov distance between a distribution and a quantizer can be performed. The exact value of the Prokhorov distance between two quantizers is obtained by solving an optimization problem through the Simplex method. This last value is used to approximate the Prokhorov distance between the two initial distributions, and the accuracy of the approximation is measured. We illustrate the method on various univariate and bivariate probability distributions. Approximation of bivariate standard normal distributions by quasi-optimal quantizers is also considered.     

A test for crossing receiver operating characteristic (roc) curves

The receiver operating characteristic (ROC) curve gives a graphical representation of sensitivity and specificity of a prediction model when varying the decision treshold on a diagnostic criterion. A classical test for comparing the overall accuracies for two models -1 and 2- is based on the difference between ROC curves areas - related to its standard error. This test is designed for the situation where ROC curve 1 caps ROC curve 2. Often both curves cross :in this paper, a new test, based on the integrated difference between the curves, is proposed to deal with this situation. In a simulation experiment, the new test was less powerful than the old test for detecting an overall superiority, but much more powerfull against the crossing alternative.     

Brain Circulation: The Educational Profile of Return Migrants

Population Research and Policy Review - Countries increasingly compete to attract and retain human capital. However, empirical studies, particularly those of migrants moving back to developing...     

The Asbestos Case: A Comment on the Appointment and Use of Nonpartisan Experts in World Trade Organization Dispute Resolution Involving Health Risk

The World Trade Organization is currently evolving its approach to incorporating scientific and technological evidence into its dispute-resolution process. In European Communities-Measures Affecting Asbestos and Asbestos-Containing Products, the Panel was faced with a large amount of complex and conflicting scientific evidence presented by the partisan experts. The Asbestos Panel's solution was to appoint independent, nonpartisan experts to help it understand and evaluate the scientific evidence. While this was far better than trying to unravel the conflicting scientific evidence on its own, two aspects of the Panel's adopted procedure merit scrutiny. First, the expert-selection process used by the Panel may not assure that the collective expertise of the appointed experts is broad enough when the dispute involves multidisciplinary scientific issues. Second, the process adopted by the Panel for consulting the appointed experts-which involved individual consultation rather than a consensus process-may leave a panel with a distorted or confused picture of the science. A consensus approach is the best means of obtaining scientific advice from appointed experts; it is most calculated to provide a clear and accurate report of the scientific information needed by a panel to make a fair and informed decision on the dispute before it. The underlying principle of world trade agreements is that it is beneficial to all of us to have free trade. Among other things, this requires an effective means of resolving disputes, and increasingly that includes disputes involving complex scientific and technological issues. This can be achieved only if the parties have confidence that their disputes will be decided in a fair and informed manner, based on the best science available. To achieve this goal, we suggest that future WTO panels depart in certain respects from the procedures utilized by the Asbestos Panel.     

Thirteen theorems in search of the truth

We review recent work on the accuracy of group judgmental processes as a function of (a) the competences (judgmental accuracies) of individual group members, (b) the group decision procedure, and (c) group size. This work on individual competence and group accuracy represents an important contribution to democratic theory and a useful complement to the usual emphasis in the social choice literature on individual preference and preference aggregation mechanisms. The work reported on is rooted in a tradition which goes back to scholars such as Condorcet, Poisson, and Bayes.     

A game theoretic approach to measuring degree of centrality in social networks

We present a new measure of degree of centrality in a social network which is based on a natural extension of the Banzhaf (1965) index of power in an N-person game.