Eaton, Morris L. - In: Journal of Multivariate Analysis 20 (1986) 2, pp. 272-276
It is shown that when the random vector X in Rn has a mean and when the conditional expectation E(u'Xv'X) = 0 for all vectors u, v [set membership, variant] Rn which satisfy u'v = 0, then the distribution of X is orthogonally invariant. A version of this characterization is also established when...