Let X1 and X2 be a random sample from B(n,p). Compute the mean and the variance of X1+X2.

Can anyone help with this one as well?

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- Dec 17th 2008, 03:41 AMPatriots326Mean and Variance
Let X1 and X2 be a random sample from B(n,p). Compute the mean and the variance of X1+X2.

Can anyone help with this one as well? - Dec 17th 2008, 03:44 AMMoo
Hello,

E(X1+X2)=E(X1)+E(X2)

For the variance :

var(X1+X2)=var(X1)+var(X2)+2 cov(X1,X2)

If X1 and X2 are independent, then cov(X1,X2)=0

After that, you have several other means, using probability density functions, moment generating functions, etc... But I don't know what you can use...