Abstract
We give formulas for the conditional and unconditional expectations of
products of multivariate Hermite and modified Hermite polynomials,
each with a multivariate normal argument. A unified approach is given
that covers both of these polynomials, each associated with a covariance
matrix. This extended Hermite polynomial is associated with a matrix
which is the difference between two covariance matrices, in other words,
with any symmetric matrix.