Optimal design: Variation in structure and performance under change of criterion

The advisability of comparing designs on the basis of several different criteria of goodness is discussed. As an illustration, designs for quadratic regression on a simplex are compared in terms of a family of criteria that includes those of A-, D- and E-optimality, as well as one of Box & Draper. Efficiency robustness under change of region, as well as of criterion, is considered. The dependence of structure of good designs on dimension is determined.