Calculate the mean deviation about median for the following data:

The class interval containing Nth 2 or 25th  item is 20−30 .  Therefore, 20−30 is the median class.  We know that  Median =l+N2−Cf×hHere, l=20,C=13,f=15,h=10 and N=50 Therefore, Median =20+25−1315×10=20+8=28Thus, mean deviation about median is given by  M.D. (M)=1N∑i=16 fixi−M=150×508=10.16