Consider discrete random variable X, with the distribution function. The variance:

\begin{tabular}{|c|c|c|c|c|c|} \hlinex & 0 & 1 & 2 & 3 & 4 \\ \hlinef(x) & 0.1 & 0.2 & 0.4 & 0.2 & 0.1 \\ \hline \end{tabular}