Hi there can anyone help me with the following:

Solve the joint distribution of X1 and X2 defined as follows

P(X1.X2=0)=1

P(Xi=1)=P(Xi=-1)=1/4 (i=1,2)

Get the expected values of X1 and X2, then their variances and covariance between them.

Any ideas?

My thoughts on expected value of X1 is the same for X2 i.e. (1/4)*1+(1/4)*-1 but that only accounts for 50% of occurence? They mention nothing about the other 50% of the time what value X1 has. Any help? Thanks