Noun
contraharmonic mean (plural contraharmonic means)
(mathematics) A type of average calculated as the arithmetic mean of the squares of the values divided by the arithmetic mean of the values, ie.
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{\displaystyle C={{(x_{1}^{2}+x_{2}^{2}+...+x_{n}^{2}) \over n} \over {(x_{1}+x_{2}+...+x_{n}) \over n}}\ or\ C(x_{1},x_{2},...,x_{n})={{x_{1}^{2}+x_{2}^{2}+...+x_{n}^{2}} \over {x_{1}+x_{2}+...+x_{n}}}}