A pharmaceutical company wants to test the effectiveness of a new drug used to treat migraine headaches. The company identifies 500 females ages 25 to 45 years old who suffer from migraine headaches. The subjects are randomly assigned into two groups. One group is given the drug and the other is given a placebo that looks exactly like the drug. After three months, the subjects’ symptoms are studied and compared.

(a) Identify the experimental units and treatments used in this experiment.

(b) Identify a potential problem with the experimental design being used and suggest a way to improve it.

(c) How could this experiment be designed to be double-blind?