  One of the remarkable notions in the recent development of quantum physics is
the weak value related to weak measurements. We emulate it as a two-time
conditional expectation in a classical stochastic model. We use the well known
symmetrized form of the master equation, which is formally equivalent to the
wave equation in quantum mechanics apart from the fact that wave functions are
always real. The origin of the unusual behaviors of the weak value such as the
negative probability and the abnormal enhancement of some expectations becomes
clearer in the present case, where the two-time conditional probability has no
ambiguity of imaginary/complex values.
