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Standard XI
Mathematics
NCERT
Question
Find the mean and variance for the following frequency distrubution
Classes
0-10
10-20
20-30
30-40
40-50
Frequencies
5
8
15
16
6
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Solution
Verified by Toppr
Class interval
f
i
x
i
u
i
=
x
i
−
A
h
u
2
i
f
i
u
i
f
i
u
2
i
0-10
5
5
-2
4
-10
20
10-20
8
15
-1
1
-8
8
20-30
15
25
0
0
0
0
30-40
16
35
1
1
16
16
40-50
6
45
2
4
12
24
Total
50
10
68
We have
N
=
∑
f
i
=
50
Width of class
h
=
10
Assumed mean
A
=
25
(
s
a
y
)
Mean,
¯
x
=
A
+
∑
5
i
=
1
f
i
u
i
N
×
h
=
25
+
10
50
×
10
=
25
+
2
=
27
⇒
¯
x
=
27
Variance
σ
2
=
h
2
⎡
⎣
∑
5
i
=
1
f
i
u
2
i
N
−
(
∑
5
i
=
1
f
i
u
i
N
)
2
⎤
⎦
σ
2
=
10
2
[
68
50
−
(
10
50
)
2
]
=
10
2
[
50
×
68
−
(
10
)
2
]
(
50
)
2
=
1
25
[
3400
−
100
]
=
3300
25
=
132
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Similar Questions
Q1
Find the mean and variance for the following frequency distrubution
Classes
0-10
10-20
20-30
30-40
40-50
Frequencies
5
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15
16
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View Solution
Q2
Find the mean, variance and standard deviation for the following frequency distribution.
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