This chapter provides the mathematical and statistical background for designs constructed by the FACTEX procedure; it also outlines the search algorithm that is used to find suitable construction rules. Note that the material in this chapter is general and theoretical; you do not need to read this chapter to use the procedure for constructing most common experimental designs. On the other hand, you should read this chapter

• to understand the general structure of designs that can be constructed with the FACTEX procedure

• to construct designs for factors with more than two levels, especially if interactions are involved

• to improve the search used by the procedure when constructing complicated designs involving many factors