Foldover is a commonly used follow-up strategy in experimental designs. All existing foldover designs were constructed by reversing the sign of columns of the initial design. We propose a new methodology by allowing the permutation of columns in foldover. Focusing on resolution IV designs, we show that almost all designs are better than existing results with respect to the minimum aberration criterion. While augmenting a design by a foldover with column permutations may result in a nonregular combined design, the proposed designs all have a resolution of 4.5 or higher, for which no two-factor interaction is fully aliased with any other two-factor interactions.
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© 2016 American Statistical Association and the American Society for Quality.
- Foldover design
- Minimum aberration design
- Optimal foldover
- Word length pattern