Construction of Mixed Column‐Orthogonal Strong Orthogonal Arrays of Strength Two Star

ABSTRACT Strong orthogonal arrays (SOAs) represent a new category of space‐filling designs that provide superior stratification compared with ordinary orthogonal arrays for computer experiments. SOAs of strength two star enhance space‐filling properties in low dimensions, particularly when column‐orthogonality is preserved. While symmetric SOAs are often the most significant for statistical applications, mixed SOAs are highly practical when factors require different numbers of levels. However, research on mixed SOAs remains limited. We introduce mixed column‐orthogonal SOAs of strength two star and present their construction methods. The proposed construction methods demonstrate both practical convenience and design flexibility. A number of mixed column‐orthogonal SOAs of strength two star can be constructed that have factors with nonprime power numbers of levels and more columns than the existing symmetric arrays. These arrays are useful for computer experiments.