Design Of Experiments, Response Surface, Spline, Box Behnken, Central Composite Design.
residuals look fine, and the plot to the left seems very fine, even though it is a saddle. However, if you remember the plot from PROC RSREG you will also realize that these results are not to be taken lightly. In fact, they should not be taken at all. Lets create a new, more simpler model. There