Find mean deviation about the mean for the following data:
 

 

$\begin{array}{l}N=\sum _{i=1}^6 f_i=40,\sum _{i=1}^6 f_i{x}_i=300,\\ \text{ Therefore }\overline{x}=\frac{1}{N}\sum _{i=1}^6 f_i{x}_i=\frac{1}{40}\times 300=7.5\\ \sum _{i=1}^6 f_i\left|x_i-\overline{x}\right|=92\\ \text{ And M.D. }\left(\overline{x}\right)=\frac{1}{N}\sum _{i=1}^6 f_i\left|x_i-\overline{x}\right|=\frac{1}{40}\times 92=2.3\end{array}$