## Standard Deviation |
September 1st, 2011 |

math |

Why isn't it:

That is, why is it the square root of the average of
`(x-mu)^2`

instead of just the average of `|x-mu|`

?
How is the squared version more useful?

**Update 2011-09-01** I had left out the square root on the standard deviation.

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