ABSTRACT
This chapter extends the results to factors at prime levels. For practical purposes, most fractionation is done on factors containing two or three levels. It consider powers of primes. The chapter discusses blocking and some irregular fractional plans. It emphasis on creating the appropriate designs. Some emphasis will be placed on the computation of mean squares, primarily through the use of computers. Prime level fractions refer to experiments performed when all factors have the same number of levels and that number is prime. Fractions of different prime levels can be constructed by working with each prime individually and crossing the resulting designs. Crossing two designs consists of running the entire second design with each design point of the first design. The concept of blocking has played a sufficiently important role in design of experiments that we decided to include a special section on it.
