Example:

Calculate the median from the following data :          

Size	Frequency
More than 50	0
“       “       40	40
“       “       30	98
“       “       20	123
“       “       10	165

 

 Solution                               

 

           

Size	Frequency	Cumulative  Frequency
40-50	40	40
30—40	58	98
20—30	25	123
10—20	42	165

Middle item is 165/2 or 82.5 which lies in 30—40 group. In this case,

The value of c = 40

L1 =30, l2=40, f1=58

M =30 +(40-30)/58(165-40)

 =30 +0.0013

M=30.0013