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power mean (Definition)

The $r$ th power mean of the numbers $x_1,x_2,\ldots,x_n$ is defined as:

$$M^r(x_1,x_2,\ldots,x_n)=\left(\frac{x_1^r+x_2^r+\cdots+x_n^r}{n}\right)^{1/r}.$$

The arithmetic mean is a special case when $r=1$ The power mean is a continuous function of $r$ and taking limit when $r\to0$ gives us the geometric mean: $$M^0(x_1,x_2,\ldots,x_n)=\sqrt[n]{x_1 {x_{2}} \cdots x_n}.$$

Also, when $r=-1$ we get $$M^{-1}(x_1,x_2,\ldots,x_n)=\frac{n}{\frac{1}{x_1}+\frac{1}{x_2}+\cdots+\frac{1}{x_n}}$$ the harmonic mean.

A generalization of power means are weighted power means.




"power mean" is owned by drini. [ owner history (1) ]
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See Also: weighted power mean, arithmetic-geometric-harmonic means inequality, arithmetic mean, geometric mean, harmonic mean, general means inequality, root-mean-square, proof of general means inequality, derivation of zeroth weighted power mean, derivation of geometric mean as the limit of the power mean, proof of arithmetic-geometric-harmonic means inequality, $\lim_{p \to \infty} \lVert x \rVert_p = \lVert x \rVert_{\infty}$


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derivation of geometric mean as the limit of the power mean (Derivation) by Mathprof
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Cross-references: weighted power means, harmonic mean, geometric mean, limit, continuous function, arithmetic mean, numbers
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This is version 9 of power mean, born on 2001-10-17, modified 2004-02-01.
Object id is 266, canonical name is PowerMean.
Accessed 7759 times total.

Classification:
AMS MSC26D15 (Real functions :: Inequalities :: Inequalities for sums, series and integrals)

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Additional References by smithpith on 2009-04-25 18:18:41
You may also be interested to read about averages, weighted averages, and means in the following book and article.

* Jane Grossman, Michael Grossman, Robert Katz. "Averages: A New Approach", ISBN 0977117049, 1983. (Available for reading at Google Book Search:
http://books.google.com/books?q=%22Non-Newtonian+Calculus%22&btnG=Search+Books&as_brr=0).

* Michael Grossman and Robert Katz. "A new approach to means of two positive numbers", International Journal of Mathematical Education in Science and Technology, Volume 17, Number 2, March 1986, pages 205 - 208.
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power mean by nctu on 2004-04-04 22:27:20
taking the limit of the power mean r->0, gives the geometric mean, please show how to achieve it.
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