Answer
$\approx4.05$
Work Step by Step
The mean of $n$ numbers is the sum of the numbers divided by $n$.
Hence the mean: $\frac{3+3+5+8+10+13 }{6}=8$
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: $\sqrt{\frac{(3-7)^2+(3-7)^2+(5-7)^2+(8-7)^2+(10-7)^2+(13-7)^2}{6-1}}\approx4.05$
