The standard deviation of a data is given by:
![\sigma=\sqrt[]{\frac{\sum ^{}_{}(x-\mu)^2}{n-1}}](https://img.qammunity.org/2023/formulas/mathematics/high-school/teq0icl3lmjoyc44xk0cgynxqam38th8ot.png)
the summation is over all the elements of the data and μ is the mean of the data, n is the number of elements.
Calculate the mean μ as follow:

Next, replace the values of the parameters into the formula for the standard deviation and simplify:
![\begin{gathered} \sigma=\sqrt[]{((5-12)^2+(8-12)^2+(11-12)^2+(13-12)^2+(17-12)^2+(18-12)^2)/(6-1)} \\ \sigma\approx5.06 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/high-school/58un5hulvjs820i3ddpy2fen61uw3khv16.png)
Hence, the standard deviation of the given data is approximately 5.06