Two varieties of corn were randomly assigned to the 8 plots in a completely
randomized design so that each variety was planted on 4 plots. Four
amounts of fertilizer (5, 10, 15, and 20 units) were randomly
assigned to the 4 plots in which variety A was planted. Likewise,
the same four amounts of fertilizer were randomly assigned to the 4
plots in which variety B was planted. Yield in bushels per acre was
recorded for each plot at the end of the experiment.