 The variance of the mean itself is

where "m" is the arithmetic mean of the reciprocals, "x" are the variates, "n" is the population size and "E" is the expectation operator.Assuming that the variance is not infinite and that the central limit theorem applies to the sample then using the delta method, the variance is

where "H" is the harmonic mean, "m" is the arithmetic mean of the reciprocals

"s"2 is the variance of the reciprocals of the data

and "n" is the number of data points in the sample.A jackknife method of estimating the variance is possible if the mean is known.