Answer
Sample variance = $s^{2}=0.1868$
Sample standard deviation = $s =0.432$
Work Step by Step
Recall the shortcut formula for calculating the variance ($s^{2}$)$:$
$$s^{2}=\frac{\sum_{i=1}^{n}x_{i}^{2}-\frac{\left(\sum_{i=1}^{n}x_{i}\right)^{2}}{n}}{n-1}$$
Plug in the given values:
$$\begin{align*}
s^{2}&= \displaystyle \frac{18-\frac{\left(17\right)^{2}}{20}}{20-1} & & \\
& =0.1868 \\\\
s&= \sqrt{0.1868} =0.432 \end{align*}$$
