Find the mean deviation about the mean for the following data: Marks obtained , 10-20, 20-30, 30-40, 40-50, 50-60, 60-70, 70-80 Number of students, 2, 3, 8, 14, 8, 3, 2

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`