The frequency distribution of marks obtained by 60 students of a class are given below:
10-20
20-30
30-40
40-50
50-60
Marks:
No. of students:
1
2
3
5
7
Marks:
60-70
70-80
80-90
90-100
1
3.
2
No. of students:
4
[Ans: 85 marks]
Calculate the average marks obtained by the students.
Answers
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Answer:
C.I f cf
0 - 10 2 2
10 - 20 10 12
20 - 30 12 24
30 - 40 15 39
40- 50 13 52
50 - 60 8 60
60 - 70 4 64
To find median, we need to find Median class first,
Total no of students(N)=64
2
N
=
2
64
=32
From Cf we can see 32 is more than 24 and less than 39, So, Median Class =30−40
Now,
M=l+
f
(
2
N
−C)
×h
where, l= lower limit of median class=30,
C= preceding cumulative frequency of median class=24,
f= frequency of median class=15,
h= class size=10
M=30+
15
32−24
×10
=30+
15
8
×10
=30+5.33=35.33
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