1. Mean 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?

2. Hello,
Originally Posted by Patriots326
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?
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...