Abstract: A criterion of design efficiency, under model uncertainty, is studied with reference to possibly nonregular fractions of general factorials. The criterion is expressed in terms of the departure of the design from being an orthogonal array of strength three or four. A Kronecker calculus for factorial arrangements facilitates the derivation. The results are followed by a numerical study and the findings are compared with those based on other design criteria.
Key words and phrases: Generalized minimum aberration, Kronecker calculus, minimum moment aberration, orthogonal array, projection.