On the construction of asymmetric orthogonal arrays

A general method for constructing asymmetric orthogonal arrays of arbitrary strength is proposed. Application of this method is made to obtain several new families of tight asymmetric orthogonal arrays of strength three. A pr ocedure for replacing a column with 2(V) symbols in an orthogonal array of strength three by several 2-symbol columns, without disturbing the orthogon ality of the array, leads to some new tight asymmetric orthogonal arrays of strength three. Some new families of asymmetric orthogonal arrays of stren gth four are also reported, and it is shown that these arrays accommodate t he maximum number of columns for given values of other parameters of the ar ray.