Find the mean deviation about the mean for the following data.

Explanation

`{(CI,x_i,fi,x_i fi),(10-20,15,2,30),(20-30,25,3,75),(30-40,35,8,280),(40-50,45,14,630),(50-60,55,8,440),(60-70,65,3,195),(70-80,75,2,150),(,,sumf_i=40,sumf_i*x_i=1800):}`
` Mean= 1800/(40) = 45`
now
also `N=40 , sumf_i|x_i - overline x|`
hence `M.D(bar x) = 400/(40) = 10`