# Symbols:V

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### Roman Numeral

- $\mathrm V$ or $\mathrm v$

The Roman numeral for $5$.

Its $\LaTeX$ code is `\mathrm V`

or `\mathrm V`

.

### Closed Set

- $V$

Frequently used, and conventionally in many texts, to denote an closed set in the context of topology.

The $\LaTeX$ code for \(V\) is `V`

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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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