Answer
$\approx2.24$
Work Step by Step
The mean of $n$ numbers is the sum of the numbers divided by $n$.
Hence the mean: $\frac{11+13+14+15+17}{5}=14$
The standard deviation of $x_1,x_2,...,x_n$ is (where $\overline{x}$ is the mean of the data values): $\sqrt{\frac{(x_1-\overline{x})^2+(x_2-\overline{x})^2+...+(x_n-\overline{x})^2}{n-1}}$.
Hence here the the standard deviation is: $\sqrt{\frac{(11-14)^2+(13-14)^2+(14-14)^2+(15-14)^2+(17-14)^2}{5-1}}\approx2.24$
