A Geometrical Interpretation of Collinearity: A Natural Way to Justify Ridge Regression and Its Anomalies

Justifying ridge regression from a geometrical perspective is one of the main contributions of this paper. To the best of our knowledge, this question has not been treated previously. This paper shows that ridge regression is a particular case of raising procedures that provide greater flexibility by transforming the matrix X associated with the model. Thus, raising procedures, based on a geometrical idea of the vectorial space associated with the columns of matrix X , lead naturally to ridge regression and justify the presence of the well-known constant k on the main diagonal of matrix X ^′ X . This paper also analyses and compares different alternatives to raising with respect to collinearity mitigation. The results are illustrated with an empirical application.     

地方高校图书馆向当地企业开展文献信息服务的可行性探讨

地方中小企业因观念、资金、技术、人才等局限,信息利用水平很低,与地方高校图书馆合作是地方企业既节约又高效获取信息服务的好途径。共建共享、信息整合、牵线搭桥、远程服务、专业导航"、镜象"服务、个性化服务等方式是地方高校图书馆向当地中小企业提供信息服务的主要途径和方法。图书馆主动与地方企业交流合作,是充分发挥信息搜集、加工、处理和传递功能,繁荣当地社会文化,服务当地经济建设,推动高校与地方经济协调发展,促进地方高校图书馆自身快速成长的明智选择。     

VAN DE HULST ON ROBUST STATISTICS: A HISTORICAL NOTE

This paper provides a discussion of an unpublished set of notes written in 1942 by the Dutch astronomer H.C. VAN DE HULST. In these notes VAN DE HULST derives the asymptotic variances of M– estimators as well as trimmed means and concludes that the asymptotic variance of what is now called HUBER'S estimator is the same as that of a trimmed mean. This conclusion is usually ascribed to BICKEL (1965). A letter written by D. VAN DANTZIG in 1943 providing a critical evaluation of. VAN DE HULST'S results, adds interest to this suprisingly early contribution to the theory of robust statistics.     

Karl Pearson—The Scientific Life in a Statistical Age by Theodore M. Porter: A Review

Porter presents an excellent account of the young Karl Pearson and his extraordinarily varied activities. These ranged from the Cambridge Mathematical Tripos Exams to German history and folklore, and included free thought, socialism, the woman's question, and the law. Returning to science, Pearson produced the famous Grammar of Science . He decided on a career in statistics only at age 35. Porter emphasizes Pearson's often acrimonious but largely successful battles to show the wide applicability and importance of statistics in many areas of science and public affairs. Eugenics became a passion for Pearson. Avoiding all formulas Porter fails to give any concrete ideas of even Pearson's most important contributions to statistical theory. We try to sketch these here.     

The Structure of Municipal Water Supply Costs: Application to a Panel of French Local Communities

Network losses and returns are importantissues for water resource management, that are addressed in thispaper by modeling the structure of production for municipal waterutilities with two outputs: water sold to final customers andwater network losses. We propose a measure of economies of scopeto assess the benefit associated with joint production of waterfor final customers and water losses, and several measures ofreturns to evaluate potential gains in exploiting technologicalflexibility of water networks. We estimate the cost structureof water utilities using a GMM procedure with a Translog costfunction and panel data. Estimation results reveal a positivedegree of economies of scope, and short-run returns to productiondensity and returns to customer density that are not significantlydifferent from 1. Significant economies of scale indicate thatlocal communities may benefit from merging into water districts.