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Math Help - [SOLVED] Mean and sd of transformation

  1. #1
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    [SOLVED] Mean and sd of transformation

    X is random variable with mean 44.584 and sd 89.265. What non zero value maust a take so that random variable given by Y=aX + a^2 has its mean equal to its sd?

    I get 44.681 but am not sure if method is correct:

    E(Y) = a*mean + a^2

    V(Y) = a^2*sd^2

    and then equate them.

    Is this right?
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  2. #2
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    Quote Originally Posted by javs156 View Post
    X is random variable with mean 44.584 and sd 89.265. What non zero value maust a take so that random variable given by Y=aX + a^2 has its mean equal to its sd?

    I get 44.681 but am not sure if method is correct:

    E(Y) = a*mean + a^2

    V(Y) = a^2*sd^2

    and then equate them.

    Is this right?
    Your method is correct (provided mean and sd^2 refer to the random variable X). I haven't checked the arithmetic.
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  3. #3
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    would sum1 mind checking that the answer is correct?
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  4. #4
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    Quote Originally Posted by javs156 View Post
    would sum1 mind checking that the answer is correct?
    It's easier (for me anyway) to check an answer (as opposed to validating a method) if the details of the calculation leading to the answer are given. Please keep that in mind for next time.

    Yes, your answer is correct.
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