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Mean and median

The mean and the median describe where the middle of a data set lies. The mean is the sum divided by the count. The median is the middle value when the numbers are sorted, and it is barely affected by a few extreme values.

xˉ=1n∑i=1nxi\bar x = \frac{1}{n}\sum_{i=1}^{n} x_imean

Symbols

xˉ\bar xmean
nnnumber of values

Example

Salaries 30, 32, 35, 36 and 200 (thousand):

mean 66.6 and median 35. The median gives a better picture of the typical salary.

If there are a few very large values, use the median.
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Part of Foundations of Mathematics: Statistics and probability.