The Shipment Times in Hours for a Load of Goods

Multiple Choice

The shipment times in hours for a load of goods from a factory to market are tabulated in the following frequency distribution. Find the sample standard deviation of shipment time. $$\begin{array} { | l | l | l | l | } \hline \text { Shipment time (hours) } & \text { Midpoint } x & \text { Frequency } f & \text { Product } x f \\\hline 22.5 - 28.5 & & 1 & \\\hline 28.5 - 34.5 & & 37 & \\\hline 34.5 - 40.5 & & 82 & \\\hline 40.5 - 46.5 & & 28 & \\\hline 46.5 - 52.5 & & 13 & \\\hline 52.5 - 58.5 & & 4 & \\\hline\end{array}$$ Round your answer to the nearest tenth.

A) 3.5 h
B) 5.5 h
C) 6.5 h
D) 4.5 h
E) 5.8 h