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KEAM 2010 Math Paper
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© examsnet.com
Question : 22
Total: 120
The mean and variance of
n
observations
x
1
,
x
2
,
x
3
,
.
.
.
,
x
n
are 5 and 0 respectively. If
n
∑
i
=
1
x
i
2
=
400
,
then the value of
n
is equal to
80
25
20
16
4
Validate
Solution:
∵
Root mean square
≥
Arithmetic mean
⇒
√
n
∑
i
=
1
x
1
2
n
≥
5
⇒
√
400
n
≥
5
⇒
400
n
≥
25
(squaring both sides)
⇒
n
≤
400
25
=
16
⇒
n
=
16
© examsnet.com
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