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TS EAMCET 5 May 2018 Shift 1 Solved Paper
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© examsnet.com
Question : 75
Total: 160
The mean and standard deviation of a distribution of weights of a group of 20 boys are 40kgs and 5kgs respectively. If two boys of weights 43kg and 37kg are excluded from this group, then the variance of the distribution of weights of the remaining group of boys is
26 , 18
5 , 27
26 , 78
7 , 17
Validate
Solution:
The mean is expressed as,
mean
=
sum of observation
n
40
=
sum of weight
20
sum of weight
=
800
The variance is calculated as,
var
=
σ
2
=
25
The new mean is
calculated as,
New mean
=
800
−
43
−
73
20
−
2
X
new
=
38
Since, variance is 25 then,
∑
x
2
20
−
(
X
)
2
=
25
∑
x
2
20
−
40
2
=
25
∑
x
2
=
32500
If two boys are removed then,
∑
x
new
2
=
32500
−
(
43
)
2
−
(
73
)
2
=
25322
The new variance is calculated as,
σ
new
2
=
∑
x
new
2
18
−
(
X
new
)
2
=
25322
18
−
(
38
)
2
=
26.78
© examsnet.com
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