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Math Help - Standard Deviation

  1. #1
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    Question Standard Deviation

    How would you explain...
    x is the standard deviation of the set of numbers (a,b,c,d,e). For each of the following sets, indicate which sets must have a standard deviation equal to x.

    (a+2, b+2, c+2, d+2, e+2)

    (a-2, b-2, c-2, d-2, e-2)

    (2a, 2b, 2c, 2d, 2e)

    (a/2, b/2, c/2, d/2, e/2)
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  2. #2
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    Re: Standard Deviation

    Quote Originally Posted by GIBETH View Post
    How would you explain...
    x is the standard deviation of the set of numbers (a,b,c,d,e). For each of the following sets, indicate which sets must have a standard deviation equal to x.

    (a+2, b+2, c+2, d+2, e+2)

    (a-2, b-2, c-2, d-2, e-2)

    (2a, 2b, 2c, 2d, 2e)

    (a/2, b/2, c/2, d/2, e/2)
    Do you know how to evaluate standard deviations? You need to square root the average of all squared deviations from the mean...
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  3. #3
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    Re: Standard Deviation

    Quote Originally Posted by GIBETH View Post
    How would you explain...
    x is the standard deviation of the set of numbers (a,b,c,d,e). For each of the following sets, indicate which sets must have a standard deviation equal to x.

    (a+2, b+2, c+2, d+2, e+2)

    (a-2, b-2, c-2, d-2, e-2)

    (2a, 2b, 2c, 2d, 2e)

    (a/2, b/2, c/2, d/2, e/2)
    The first 2 do.

    Think about what the standard deviation actually measures.
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  4. #4
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    Re: Standard Deviation

    Standard deviation measures spread about the mean. Adding 2 to each value also increases the mean by 2 so difference between each value and the mean does'nt change. Hence standard deviation doesn't change. Similarly when subtracting 2.
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