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Student2013
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The distribution of men's heights has a mean of 68in, standard deviation of 2.5in.

If the heights of brothers have a correlation of 0.5, what is the mean and variance of the difference in heights between pairs of brothers?

 

I know that r=Cov(x,y)/(sqrt(V(x)V(y))

so 0.5=Cov(x,y)/(sqrt(2.52)(V(y))

but then I'm stuck trying to solve the Cov since they arent independent, E(xy) does not equal E(x)E(y)

 

 

I have the solution, can't see how to get there.

The solution: mean=0, variance=6.25

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