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The standard deviation of n obervations ...

The standard deviation of n obervations `x_(1),x_(2).....,x_(n)` is 2. If `sum_(i=1)^(n)x_(i)=20andsum_(i=1)^(n)x_(i)^(2)=100`, then n is

A

10 or 20

B

5 or 10

C

5 or 20

D

5 or 15

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