Approximate the Variance and Standard Deviation of a Variable from Grouped

Multiple Choice

Approximate the Variance and Standard Deviation of a Variable from Grouped Data
-For the following data set, approximate the sample standard deviation of emails per day. $\begin{array}{c|c}\text { Emails (per day) } & \text { Frequency } \\\hline 8-11 & 18 \\12-15 & 23 \\16-19 & 38 \\20-23 & 47 \\24-27 & 32\end{array}$

A) $5.1$ emails
B) $4.0$ emails
C) $25.8$ emails
D) $19.3$ emails