Connections between two-level designs of resolutions III and V

Resolution III* designs are resolution III designs in which no two-factor interactions are confounded with one another. They arise naturally in the search for small composite designs and were first suggested by Hartley (1959). New results given here link resolution III* designs to resolution V designs, enabling passage between the two types of designs to be made. This means that previously untabulated resolution III* designs can be derived directly from known resolution V designs. For example, a Hartley-type composite design can be based on a 27−1 III* design (derived from a 26−1 V design); the “usual” composite design is based on a 27−1 V design, double the number of factorial runs. The resolution III* designs can also be usefully modified for specific industrial applications (Box and Jones 1989). Moreover, the maximum number of factors it is possible to accommodate in a resolution III* design of a given size can be obtained directly from the known maximum for resolution V designs of the same size.