Thank you CaptainBlack. My problem is the result on the book is different. It says covariance= 59.17
But according to the calculations of excel
and E(X)=53 and E(Y)= 55
So 2946.66- 53*55= 31.66
We know thatOriginally Posted by 0123
covar(X,Y) =E(XY) - E(X)E(Y)
so we need only evaluate these expaectations.
The probabilities p(45,40), .. are derived from the requirement that all the
probabilities sum to 1.
The remaing calcs are shown in the attached image of the spreadsheet.