Calculate the Standard Deviation of X for the Probability Distribution

Short Answer

Calculate the standard deviation of X for the probability distribution.
Please round your answer to the nearest whole number, if necessary. $$\begin{array} { | c | c | c | c | c | c | c | } \hline x & - 5 & - 2 & 0 & 3 & 6 & 9 \\\hline P ( X = x ) & 0.2 & 0.3 & 0.2 & 0.1 & 0 & 0.2 \\\hline\end{array}$$ ​ $$\sigma =$$ __________