Frequency Distribution of the Scores from a Mathematics Test Is

Short Answer

Frequency distribution of the scores from a mathematics test is given in the table below. Find the sample standard deviation.
  $$\begin{array} { | l | l | l | l | } \hline \text { Interval } & \text { Midpoint } x & \text { Frequency } f & \text { Product } x f \\\hline 58.5 - 65.5 & & 3 & \\\hline 65.5 - 72.5 & & 5 & \\\hline 72.5 - 79.5 & & 8 & \\\hline 79.5 - 86.5 & & 6 & \\\hline 86.5 - 93.5 & & 3 & \\\hline 93.5 - 100.5 & & 5 & \\\hline\end{array}$$  
Please round your answer to the nearest whole number, if necessary.