Find the range, mean, variance, and standard deviation of the sample data set.
The durations (in days) of pregnancies for a random sample of mothers
$\begin{array}{ccccc}295 & 280 & 268 & 278 & 291\end{array}$
$277 \quad 291$
$\begin{array}{rrrrr}279 & 296 & 285 & 269 & 293\end{array}$
$277 \quad 282$
$\begin{array}{rrrr}267 & 281 & 286 & 269\end{array}$
$264 \quad 299$