Estimating the covariance matrix: a new approach

  • Authors:
  • T. Kubokawa;M. S. Srivastava

  • Affiliations:
  • Faculty of Economics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan;Department of Statistics, University of Toronto, 100 St. George Street, Toronto, Ont., Canada M5S 3G3

  • Venue:
  • Journal of Multivariate Analysis
  • Year:
  • 2003

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Abstract

In this paper, we consider the problem of estimating the covariance matrix and the generalized variance when the observations follow a nonsingular multivariate normal distribution with unknown mean. A new method is presented to obtain a truncated estimator that utilizes the information available in the sample mean matrix and dominates the James-Stein minimax estimator. Several scale equivariant minimax estimators are also given. This method is then applied to obtain new truncated and improved estimators of the generalized variance; it also provides a new proof to the results of Shorrock and Zidek (Ann. Statist. 4 (1976) 629) and Sinha (J. Multivariate Anal. 6 (1976) 617).