Smokers may have a more difficult time quitting smoking if they live with another smoker. How can an experiment explore this possibility in a study to compare bupropion with placebo? Suppose the researchers split the subjects into two groups: those who live with another smoker, and those who do not live with smokers. Within each group, the subjects are randomly assigned to take bupropion or a placebo. The figure shows a flow chart of this design, when 250 of the 429 study subjects live with nonsmokers and 179 live with another smoker.
a. Is this design a completely randomized design? Why or why not?
b. Does this experiment have blocks? If so, identify them.
c. Is this design a randomized block design? Explain why or why not.

Experimental Units: 429 Smokers Block the subjects according to whether they live with a smoker. Block 1 Does Not Live with Smoker (n = 250) Block 2 Lives with Smoker (n 179) Randomly assign to a treatment group. Randomly assign to a treatment group. Treatment Treatment 2 Treatment1 Treatment 2 (125 subjects 125 subjects) (90 subjects) (89 subjects) Compare the two treatment Bupropion Placebo Bupropion Placebo Compare the two treatment percentages of those who percentages of those who have relapsed. have relapsed.