Question

find the missing frequencies if N=100 and median is 32.
marks obtained-0-10, 10-20, 20-30, 30-40, 40-50, 50-60, total
no. of students-10 ,? ,25 ,30 ,? ,10 ,100.
What is mean mark

Answer 1

let the missing frequencies be x and y

cumulative frequency

10

10+x

35+x

65+x

65+x+y

75+x+y

given: n=100 , n/2=50 (n=75+x+y, therefore x+y=25)

median=32 therefore the class interval is 30-40

l=30, cf=35+x, f=30, h=10

median=l+[(n/2-cf) /f ]*h

32=30+[50-(35+x)/30]*10

32=(90+50-35-x)/3

96=105-x

x=9

9+y=25

y=16

Hope this helps!