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 unused vacation days. $\begin{array}{c|c}\text { Days } & \text { Frequency } \\\hline 1-2 & 9 \\3-4 & 12 \\5-6 & 8 \\7-8 & 5 \\9-10 & 4\end{array}$

A) $2.6$ days
B) $2.5$ days
C) $6.5$ days
D) $6.6$ days