Editing Harmonic mean (section)

===Delta method===
{{Unreferenced section|date=December 2019}}

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

: <math>\operatorname{Var}(H) = \frac{1}{n}\frac{s^2}{m^4}</math>

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

: <math>m = \frac{1}{n} \sum{ \frac{1}{x} }.</math>

''s''<sup>2</sup> is the variance of the reciprocals of the data

: <math>s^2 = \operatorname{Var}\left( \frac{1}{x} \right) </math>

and ''n'' is the number of data points in the sample.