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Questions  >>  JEEMAIN and NEET  >>  Mathematics  >>  Class12  >>  Probability
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Q)

If the variance of the random variable X is 9, the standard deviation of the random variable -4x+8 is?

(A) 144

(B) 27

(C) 12

(D) 16

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A)

If variance of a random variable X is "K"..                    

Now for a random variable aX+b the variance is (a)^2 times K.

Now,given

variance of the random variable X is 9 thenstandard deviation of the random variable -4x+8 .

now Comparing this with ax+b  a=-4

       (-4)^2=16

       new variance is 16x9=144.

     But standard deviation is square root of variance.

     So,square root of 144 is 12.

    so answer is C-12

 

 

 

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