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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

`sqrt(5)`

D

`(3)/(2)`

Text Solution

Verified by Experts

Standard deviation.
`= sqrt((sum_(j=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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