Three skin cleansing agents were used on three persons. For each person, three patches of skin were exposed to a contaminant and afterward cleansed by using one of the three cleansing agents. After 8 hours, the residual contaminant was measured, with the following results:
SST = 1.18, SSB = .78, SSE = 2.24.
a What are the experimental units, and what are the blocks in this experiment?
b Test the hypothesis that there are no differences among the treatment means, using α=.05.