suppose that you want to conduct a randomized block experiment. There are four
textbooks which could be used for a particular subject, and you want to see which books help
the students to have higher test scores. You decide to randomly assign one of the books to
each of four sections of the class in the fall semester. However, you realize that the
composition of the class changes from one semester to the next, so you decide to use three
semesters (fall, spring, and summer) as blocks. The semesters are ordered; we can't randomly
assign spring to come after summer, for example. However, within each semester, we can
randomize the textbooks to the four sections of the class. Consider the following SAS program.