Question: Show in (*) that the left hand side (formula for the variance of a population) of the equation below is the same as the right hand side: i.e.

(*) =

In order to show this, multiply out the square in the numerator of the left hand side and you use the fact that

and .

You may also have observed that the right hand side of the above is also equal to:

= .

This is a better formula than . The reason is that if the x's are whole numbers and the ?'s are not, we are squaring whole numbers and adding them instead of squaring decimal numbers.