Definition:Degenerate Distribution

Definition
Let $X$ be a discrete random variable on a probability space.

Then $X$ has a degenerate distribution with parameter $r$ if:


 * $\Omega_X = \left\{{r}\right\}$

1 & : k = r \\ 0 & : k \ne r \end{cases}$
 * $\Pr \left({X = k}\right) = \begin{cases}

That is, there is only value that $X$ can take, namely $r$, which it takes with certainty.

It trivially gives rise to a probability mass function satisfying $\Pr \left({\Omega}\right) = 1$.

Equally trivially, it has an expectation of $r$ and a variance of $0$.