Answer
$R=25~min$
$s=8.43~min$
Work Step by Step
$R=largest~data~value-smallest~data~value=282-257=25$
The mean:
$x̅=\frac{282+270+260+266+257+260+267}{7}=266$
The standard deviation:
$s=\sqrt {\frac{Σ(x_i-x̅)^2}{n-1}}=\sqrt {\frac{(282-266)^2+(270-266)^2+(260-266)^2+(266-266)^2+(257-266)^2+(260-266)^2+(267-266)^2}{7-1}}=8.43$
