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    I have worked out the Variance, but the mark scheme them says to multiply it by 4?

    Any ideas why? (The variance is 72.9166...)

    Thanks,
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    (Original post by lindseyyy)
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    I have worked out the Variance, but the mark scheme them says to multiply it by 4?

    Any ideas why? (The variance is 72.9166...)

    Thanks,
    The question refers to even numbers - are you sure they haven't scaled things.

    E.g. if the numbers are 2, 4, 6 then they are twice the numbers 1, 2, 3 which are are uniform discrete from 1 to 3. Your book probably tells you what the variance of this is, but if Y represents the original numbers and X the numbers 1, 2, 3 then Y = 2X and you should have a rule that says Var(Y) = Var(2X) = 4Var(X)
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    As Davros said..

    You need 4\times \frac{30^2-1}{12}

    That should be 4 x 74.9166 rather than 4 x 72.9166.
 
 
 
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