From the Data Below on the 600-Yard Walk-Run Test (Time

Short Answer

From the data below on the 600-yard walk-run test (time in seconds), calculate the standard deviation.
$$\begin{array} { | l | l | l | } \hline \text { Group } X & f & \\\hline & & - \\\hline 266 - 280 & 5 & X = 160.69 \\\hline 251 - 265 & 17 & \\\hline 236 - 250 & 28 & \\\hline 221 - 235 & 33 & \\\hline 206 - 220 & 38 & \\\hline 191 - 205 & 67 & \\\hline 176 - 190 & 103 & \\\hline 161 - 175 & 164 & \\\hline 146 - 160 & 180 & \\\hline 131 - 145 & 151 & \\\hline 116 - 130 & 144 & \\\hline 101 - 115 & 66 & \\\hline 86 - 100 & 15 & \\\hline\end{array}$$