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Math Help - Variance question

  1. #1
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    Variance question

    Hi - I'm stuck on this question:

    Given the following sample of three measurements,

    10.0 15.2 17.2
    what value must be added to the sample to make a new sample having double the variance of these three measurements?

    I know the formula for the sample variance but have no idea of how to calculate the new added value....

    Any help would be greatly appreciated.

    F
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  2. #2
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    Re: Variance question

    Quote Originally Posted by FelixHelix View Post
    Hi - I'm stuck on this question:

    Given the following sample of three measurements,

    10.0 15.2 17.2
    what value must be added to the sample to make a new sample having double the variance of these three measurements?

    I know the formula for the sample variance but have no idea of how to calculate the new added value....

    Any help would be greatly appreciated.

    F
    Calculate the variance of 10.0 15.2 17.2. Call the number a.

    Calculate the variance of 10.0 15.2 17.2 x. Call the result b. It will have x in it.

    Solve b = 2a for x.
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