Projective three-level main effects designs robust to model uncertainty

This paper is concerned with designing experiments under the assumption tha t an analysis strategy is used that considers interactions in addition to m ain effects. A criterion which averages an approximation to A(s)-efficiency over lower-dimensional projections of the design is introduced to compare designs. A columnwise design procedure is used to construct three-level des igns for six factors in 18 runs. The projection effciencies of these design s are explored and compared with designs obtained from the L-18 orthogonal array. Results are also given for designs with 14 and 17 runs.