Tight Bounds On Expected Order Statistics

  • Authors:
  • Dimitris Bertsimas;Karthik Natarajan;Chung-Piaw Teo

  • Affiliations:
  • Sloan School of Management and Operations Research Center, Massachusetts Institute of Technology, Cambridge, MA 02139, E-mail: dbertsim@mit.edu;Department of Mathematics, National University of Singapore, Singapore 117543, E-mail: matkbn@nus.edu.sg;Department of Decision Sciences, NUS Business School, Singapore 117591, E-mail: bizteocp@nus.edu.sg

  • Venue:
  • Probability in the Engineering and Informational Sciences
  • Year:
  • 2006

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Abstract

In this article, we study the problem of finding tight bounds on the expected value of the kth-order statistic E [Xk:n] under first and second moment information on n real-valued random variables. Given means E [Xi] = &mgr;i and variances Var[Xi] = σi2, we show that the tight upper bound on the expected value of the highest-order statistic E [Xn:n] can be computed with a bisection search algorithm. An extremal discrete distribution is identified that attains the bound, and two closed-form bounds are proposed. Under additional covariance information Cov[Xi,Xj] = Qij, we show that the tight upper bound on the expected value of the highest-order statistic can be computed with semidefinite optimization. We generalize these results to find bounds on the expected value of the kth-order statistic under mean and variance information. For k n, this bound is shown to be tight under identical means and variances. All of our results are distribution-free with no explicit assumption of independence made. Particularly, using optimization methods, we develop tractable approaches to compute bounds on the expected value of order statistics.