# Variance

A measure of the average deviation from the average value

1. of a sample

Given a sample of $$n$$ values $$x_i$$ with mean $$\mu$$, the variance is defined as
$\frac{1}{n}\sum_{i=1}^{n}\left(x_i - \mu\right)^2$
where $$\sum$$ is the summation sign.

2. of a distribution

For a random variable $$X$$ with the distribution in question and having a mean of $$\mu$$, the variance is equal to the expectation of the function
$f(X) = \left(X - \mu\right)^2$

### Gallimaufry

 AKCalc ECMA Endarkenment Turning Sixteen

This site requires HTML5, CSS 2.1 and JavaScript 5 and has been tested with

 Chrome 26+ Firefox 20+ Internet Explorer 9+