Answer
$\approx1.55$
Work Step by Step
The mean of $n$ numbers is the sum of the numbers divided by $n$.
Hence the mean: $\frac{18+19+19+18+17+18+20+21+20+22}{5}=19.2$
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: $\sqrt{\frac{(17-19.2)^2+3(18-19.2)^2+2(19-19.2)^2+2(20-19.2)^2+(21-19.2)^2+(22-19.2)^2}{10-1}}\approx1.55$
