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      last updated: 2003-12-20T08:38:08Z
      updated by: Charles Matthews
      
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Given a set of data, X={x<sub>1</sub>, x<sub>2</sub>, ..., x<sub>n</sub>} and corresponding weights, W={w<sub>1</sub>, w<sub>2</sub>, ..., w<sub>n</sub>} the '''weighted mean''' is calculated as

:<math>
\bar{x} = \frac{ \sum_{i=1}^n w_i \cdot x_i}{\sum_{i=1}^n w_i}
</math>

Note that if all the weights are equal, the weighted mean is the same as the [[arithmetic mean]].

back to [[summary statistics]] -- [[central tendency]]

'''See also:''' [[average]]

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====References====
* Adapted from the [[Wikipedia]] article, "Weighted_mean" [http://en.wikipedia.org/wiki/Weighted_mean http://en.wikipedia.org/wiki/Weighted_mean], used under the [[GNU Free Documentation License]]