  We provide a unified description of efficiency correction and error
estimation for moments of conserved quantifies in heavy-ion collisions. Moments
and cumulants are expressed in terms of the factorial moments, which can be
easily corrected for the efficiency effect. By deriving the covariance between
factorial moments, one can obtain the general error formula for the efficiency
corrected moments based on the error propagation derived from the Delta
theorem. The skellam distribution based Monto Carlo simulation is used to test
the Delta theorem and Bootstrap error estimation methods. The statistical
errors calculated from the two methods can well reflect the statistical
fluctuations of the efficiency corrected moments.
