Question

Find four moments
about the
mean
for the
following data.
C.I
10-20
20-30
30-40
40-50
50-60
60-70
70-80
frequency
z
15
35
60
84
96
127
198
250​

Answer 1

Answer:

Marks (x) No. of students (f) C.F.

0-10 15 15

10-20 20 35

20-30 25 60

30-40 24 84

40-50 12 96

50-60 31 127

60-70 71 198

70-80 52 250

N = 250

As, N=250⇒

2

N

=

2

250

=125

As 127 is just greater than 125, therefore median class is 50−60.

Median=l+

f

2

N

+C

×h

Here, l=lower limit of median class =50

C=C.F. of the class preceding the median class =96

h= higher limit - lower limit =60−50=10

f= frequency of median class =31

∴median=50+

31

125−96

×10=50+9.35=59.35