# Symbols:V/Variance

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## Variance

- $\var X$

Let $X$ be a discrete random variable.

Then the **variance of $X$**, written $\var X$, is a measure of how much the values of $X$ vary from the expectation $\expect X$, and is defined as:

- $\var X := \expect {\paren {X - \expect X}^2}$

That is: it is the expectation of the squares of the deviations from the expectation.

The $\LaTeX$ code for \(\var X\) is `\var X`

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