On matrix variance inequalities

Olkin and Shepp [2005, A matrix variance inequality. J. Statist. Plann. Inference 130, 351-358] presented a matrix form of Chernoff's inequality for Normal and Gamma (univariate) distributions. We extend and generalize this result, proving Poincaré-type and Bessel-type inequalities, for matrices of arbitrary order and for a large class of distributions.