3. Fifty patients suffering from knee pain have volunteered to participate in an experiment to examine the effects of pain relief medication. Half will be assigned to take 400 mg of the pain reliever every six hours, and the other half to take 200 mg every 3 hours. The patients will report their pain levels on a 1-10 scale at the beginning of the experiment and again after 8 days on the medication. a) Define the experimental units and the response variable. b) What are the treatments? c) Describe an appropriate method to assign the volun- teers to treatments. d) An alternate design could include a control group who take a placebo. Describe an advantage of adding a control group