We evaluate a typical value of higher-order cumulants (irreducible moments) of conductance fluctuations that could be extracted from magnetoconductance measurements in a single sample when an external magnetic field is swept over an interval B0. We find that the nth cumulant has a sample-dependent random part ±〈〈g2〉〉n/2sqrt[anBc/Bo], where 〈〈g2〉〉 is the variance of conductance fluctuations, Bc is a correlation field, and an∼n! This means that an apparent deviation of the conductance distribution from a Gaussian shape, manifested by nonvanishing higher cumulants, can be a spurious result of correlations of conductances at different values of the magnetic field.