There have been anecdotal reports of the ability of duct tape to remove warts. In an experiment conducted at the Madigan Army Medical Center in the state of Washington (Archives of Pediatric and Adolescent Medicine 2002; 156: 971–974), 51 patients between the ages of 3 and 22 were randomly assigned to receive either duct-tape therapy (covering the wart with a piece of duct tape) or cryotherapy (freezing a wart by applying a quick, narrow blast of liquid nitrogen). After two months, the percentage successfully treated was 85% in the duct tape group and 60% in the cryotherapy group.
a. Identify the response variable, the explanatory variable, the experimental units, and the treatments.
b. Describe the steps of how you could randomize in assigning the 51 patients to the treatment groups.