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If x(1), x(2),"…......." x(18) are obser...

If `x_(1), x_(2),"…......." x_(18)` are observation such that `sum_(j=1)^(18)(x_(j) -8) = 9` and `sum_(j=1)^(18)(x_(j) -8)^(2) = 45`, then the standard deviation of these observations is

A

`sqrt((81)/(34))`

B

5

C

`sqrt5`

D

`(3)/(2)`

Text Solution

Verified by Experts

The correct Answer is:
D
Standard devivation
`=sqrt((sum_(f=1)^(18)(x_(j)-8)^(2))/(n)-((sum_(j=1)^(18)(x_(j)-8))/(n))^(2))=sqrt((45)/(18)-((9)/(18))^(2))=sqrt((45)/(18)-(1)/(4))=sqrt((81)/(36))=(9)/(6)=(3)/(2)`
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