When finding the variance where did the '2' go in the second terrm of the third step and why do we mulitply another 'n' to last term how do we get it? this is the answer to exercise 15.2 question2 provided by meritnation....
The said term is
Since does not have i, so it can be taken out of the summation as summation is taken over i = 1, 2, ..., n.
So,
Hope you will get this step now!