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Math Help - [SOLVED] Random Variables

  1. #1
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    [SOLVED] Random Variables

    The random variable T has the:
    Mean 20
    Standard deviation 5

    It is required to scale T by using the transformation S = aT + b where a and b are constants ( a > 0 ) so that E ( S ) and Var ( S ) satisfy specified values.

    Find the value of a and b in this particular case:

    when E ( S ) = 0
    and when Var ( S ) = 1
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  2. #2
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    Try these numbers in your equations

    Your original mean is 20. So subtract 20 from all the numbers to get a mean of 0.

    Your original std deviation is 5, So scale by 1/5 to reduce the std deviation to 1.

    These combine to a transformation of (1/5)x -20.
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  3. #3
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    Random Variables

    I see what you mean, but the transformation says + b, and you've used a minus (-20 ) =/
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  4. #4
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    The standard language is such that +B means add some constant. There is no constraint that the constant be positive unless the language says "add a positive constant". So negatives are fine. In the future, you might have to add a complex number, which is neither positive nor negative.
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  5. #5
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    Random Variables

    that makes sense, i understandd now, thank you for the help
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