English

An inequality for expectation of means of positive random variables

Probability 2017-02-22 v1

Abstract

Suppose that X,YX,Y are positive random variable and mm a numerical (commutative) mean. We prove that the inequality E(m(X,Y))m(E(X),E(Y)){\rm E} (m(X,Y)) \leq m({\rm E} (X), {\rm E} (Y)) holds if and only if the mean is generated by a concave function. With due changes we also prove that the same inequality holds for all operator means in the Kubo-Ando setting. The case of the harmonic mean was proved by C.R. Rao and B.L.S. Prakasa Rao.

Keywords

Cite

@article{arxiv.1608.08671,
  title  = {An inequality for expectation of means of positive random variables},
  author = {Paolo Gibilisco and Frank Hansen},
  journal= {arXiv preprint arXiv:1608.08671},
  year   = {2017}
}