Mixed 2-and 2r-level fractional factorial split-plot designs with clear effects

Fractional factorial split-plot (FFSP) designs are often used when the levels of some factors are difficult to change or control. If not all experimental factors have the same number of levels, mixed-level designs are natural choices. This paper provides the necessary and sufficient conditions for mixed 2- and 2(r)-level FFSP designs of resolution III or IV to contain clear main effects or two-factor interaction components. Particularly, the sufficient conditions are proved through constructing the corresponding designs. The new results here are more general and include Zhao and Chen (2012a,b)'s results as special cases for r = 2. (C) 2019 Elsevier B.V. All rights reserved.