Approximate the Sample Standard Deviation Given the Following Frequency Distribution

Multiple Choice

Approximate the sample standard deviation given the following frequency distribution.

$\begin{array} { c c } \hline \text { Class } & \text { Frequency } \\\hline 0 - 19 & 10 \\20 - 39 & 18 \\40 - 59 & 10 \\60 - 79 & 8 \\80 - 99 & 13 \\\hline\end{array}$

A) 798.2
B) 28.3
C) 28.5
D) 811.9