Chapter 15.9, Problem 1E

1-16. Find the sample standard deviation for each set of measurements in Exercises 1–16 of Exercises 15.8.

From the following grouped data, find the mean.

$\text{Interval}$	$\begin{array}{l}\text{Midpoint}\\ x\end{array}$	$\begin{array}{l}\text{Frequency}\\ f\end{array}$	$\begin{array}{l}\text{Product}\\ xf\end{array}$
41.5-48.5		12
48.5-55.5		15
55.5-62.5		20
62.5-69.5		25
69.5-76.5		4
76.5-83.5		2