Consider a design. Suppose after running the experiment, the largest observed effects are A + BD, B + AD, and D + AB. You wish to augment the original design with a group of four runs to de-alias these effects.
(a) Which four runs would you make?
(b) Find the variances and covariances of the regression coefficients in the model
![1772_8f5a993f-db1b-43fd-93f5-0882d3436f4d.png](https://secure.tutorsglobe.com/CMSImages/1772_8f5a993f-db1b-43fd-93f5-0882d3436f4d.png)
(c) Is it possible to de-alias these effects with fewer than four additional runs?