10.15. Suppose that we are fitting a straight line and we desire to make the variance of as small as possible.

Restricting ourselves to an even number of experimental points, where should we place these points so as to minimize V( )? [Note: Use the design called for in this exercise with great caution because, even though it minimizes V( ), it has some undesirable properties; for example, see Myers, Montgomery and Anderson-Cook (2009). Only if you are very sure the true functional relationship is linear should you consider using this design.]