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Math Help - can someone verify if I did this correctly ?

  1. #1
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    can someone verify if I did this correctly ?

    1. Var(x)=4
    find Var((1-x)/2)

    I did: Var((1-x)/2) = Var(0.5*(1-x)) = 0.25*Var(1-x) = 0.25*Var(-x) =
    0.25*Var(x)=0.25*4=1

    2. regression question: B(y/x) = -0.625 , B(x/y)=-0.4 . Find r.
    I did:

    B(y/x)=r*(Sy/Sx) B(x/y)=r*(Sx/Sy)
    -0.625=r*s
    -0.4 = r/s
    .
    .
    .
    r=-0.5

    Are these two correct ?

    thanks a million !
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  2. #2
    MHF Contributor matheagle's Avatar
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    The first one is OK
    In the second one, I have no idea what these B's are.
    Killer B's?
    Last edited by matheagle; May 23rd 2010 at 03:29 PM.
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  3. #3
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    the B's are the regression coefficients. B(y/x) is the coefficient of X when Y is the response, and when B(x/y) it's the opposite.
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