1. Compare these two types of screening designs: the 2^k-p fractional factorial designs (n= 4, 8, 16, 32, etc) and the Plackett-Burman designs that are not a power of two (eg, n= 12, 20, 24, 28, etc).

a. What is similar about these two types of designs? (Hint:It involves their balance and orthogonality properties, which you should describe).

b. What is the main difference between these two types of designs? (Hint: It involves how they are affected by two factor interactions.)