Answer
$\approx2.34$
Work Step by Step
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: $\sqrt{\frac{(3-3.67)^2+(6-3.67)^2+(2-3.67)^2+(1-3.67)^2+(7-3.67)^2+(3-3.67)^2}{6-1}}\approx2.34$
