  We evaluate a typical value of higher order cumulants (irreducible moments)
of conductance fluctuations that could be extracted from magneto-conductance
measurements in a single sample when an external magnetic field is swept over
an interval $B_0$. We find that the n-th cumulant has a sample-dependent random
part $\pm \gN 2^{n/2}\sqrt{a_{n}B_{c}/B_{0}}$, where $\gN 2$ is the variance of
conductance fluctuations, $B_{c}$ is a correlation field, and $a_{n}\sim n!$.
This means that an apparent deviation of the conductance distribution from a
Gaussian shape, manifested by non-vanishing higher cumulants, can be a spurious
result of correlations of conductances at different values of the magnetic
field.
