Some Problems with Conditional Probability and Quasimoment Functions

General formulas are obtained for a posteriors quasimoment functions and, consequently, for semi-invariants. These formulas enable forecasting and filtration problems to be solved. The solution is expressed in the form of series through a priori quasimoment functions and Hermite's multidimensional polynomials. The conditions for convergence of these series are not investigated.