Adrug researcher wishes to test a new pain medication for effectiveness in treating the pain associated with arthritis. 20 of 40 severely disabled arthritis sufferers in a hospital ward will receive the drug. the other 20 will receive a placebo. the experimenters do not know whether any given subject receives the drug or the placebo.
which of the following principles of experimental design are being followed in this experiment? check all that apply.
a. confounding
b. blocking
c. control
d. replication
e. blindness