The second-order metamodel for the inventory model given by Eq. (12.10) had  and seemed to...

The second-order metamodel for the inventory model given by Eq. (12.10) had  and seemed to provide a reasonably good representation of the “true” response surface shown in Fig. 12.8. On the other hand, the metamodel given by Eq. (12.7) had  but provided a poor representation of the true response surface. How is this possible given the widespread reliance on R² statistics?

FIGURE 12.8 (a) Response-surface plot and (b) contour plot from direct simulation of the inventory model.