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METHODS FOR SYMMETRIZING RANDOM VARIABLES

Published online by Cambridge University Press:  19 August 2010

Christopher S. Withers
Affiliation:
Applied Mathematics Group, Industrial Research Limited, Lower Hutt, New Zealand E-mail: c.withers@irl.cri.nz
Saralees Nadarajah
Affiliation:
School of Mathematics, University of Manchester, Manchester M13 9PL, UK E-mail: mbbsssn2@manchester.ac.uk

Abstract

Let X be a random variable with nonsymmetric density p(x). We give the symmetric density q(x) closest to it in the sense of Kulback–Liebler and Hellinger distances. (All symmetries are around zero.) For the first distance, we show that q(x) is proportional to the geometric mean of p(x) and p(−x). For example, a symmetrized shifted exponential is a centered uniform, and a symmetrized shifted gamma is a centered beta random variable. For the second distance, q(x) is proportional to the square of the arithmetic mean of p(x)1/2 and p(−x)1/2. Sample versions are also given for each. We also give the optimal random function f such that f(X) is symmetrically distributed and minimizes |f(X)−X|. Finally, we show how to optimize the Hellinger distance for vector X subject to supersymmetry and for scalar X subject to being monotone about zero in each half-line.

Type
Research Article
Copyright
Copyright © Cambridge University Press 2010

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References

1.Al-Awadhi, F., Konsowa, M. & Najeh, Z. (2009). Commute times and the effective resistances of random trees. Probability in the Engineering and Informational Sciences 23: 649660.CrossRefGoogle Scholar
2.Azzalini, A. (1985). A class of distributions include the normal ones. Scandinavian Journal of Statistics 12: 171178.Google Scholar
3.Coffman, E.G., Flajolet, P., Flatto, L. & Hofri, M. (1998). The maximum of a random walk and its application to rectangle packing. Probability in the Engineering and Informational Sciences 12: 373386.CrossRefGoogle Scholar
4.Fisher, N.I. (1993). Statistical analysis of circular data. Cambridge: Cambridge University Press.CrossRefGoogle Scholar
5.Kullback, S. (1959). Information theory and statistics. New York: Wiley.Google Scholar
6.Kullback, S. & Leibler, R.A. (1951). On information and sufficiency. Annals of Mathematical Statistics 22: 7986.CrossRefGoogle Scholar
7.Nikulin, M.S. (2001). Hellinger distance. In Hazewinkel, M. (ed.), Encyclopaedia of mathematics. Amsterdam: Kluwer Academic.Google Scholar
8.Silverman, B.W. (1986). Density estimation for statistics and data analysis. New York: Chapman & Hall.Google Scholar