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Average height & variance of 5 students ...

Average height & variance of `5` students in a class is `150` and `18` respectively. A new student whose height is `156 cm` is added to the group. Find new variance. (a) `20` (b) `22` (c) `16` (d) `14`

A

22

B

20

C

18

D

16

Text Solution

Verified by Experts

The correct Answer is:
B
`(sumX^(2))/5-150^(2)=180=sumX^(2)=90+5xx150^(2)`
New mean `=151` cm
New `sumX^(2)=90+5xx150^(2)+156^(2)`
New variance `=1/6(90+5xx150^(2)+156^(2))-151^(2)=20`
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