Let $X \in \text{Random}(\mathbb{R}^{N \times 1})$ be a D5210: Random real column matrix such that

(i)	\begin{equation} \mathbb{E} \Vert X \Vert^2_2 < \infty \end{equation}

Then \begin{equation} \mathbb{E} \Vert X - \mathbb{E} X \Vert^2_2 = \mathbb{E} \Vert X \Vert^2_2 - \Vert \mathbb{E} X \Vert^2_2 \end{equation}