  One calls attention to the fact that the stochastic physical systems are not
random completely. They have both random and regular components of their
evolution. Dynamic system is considered to be a special case of physical system
with vanishing stochastic component of evolution. Mathematical technique for
description of regular evolution component of physical systems (stochastic and
deterministic) is constructed. The regular component of the system S evolution
is described explicitly by the statistical average system <S>, which is a
continuous dynamic system. The action for <S> is reduced to the form of the
action for a set of interacting identical deterministic systems S_d. The form
of interaction of S_d describes implicitly the character of the stochastic
component of S evolution. Interplay between the physical system S and the
statistical average system <S> in the measurement process is discussed. There
are at least two different kind of measurement: single measurements
(S-measurements) connected with measurements in S and mass measurements
(M-measurements) connected with measurements in <S>. Conventional
identification of S-measurement and M-measurement is a source of many
misunderstandings and paradoxes.
