Sickle-cell disease is a painful disorder of the red blood cells. To investigate whethera new drug can reduce the pain associated with sickle-cell disease, a study by the National Institutes of Healthrandomly assigned 150 sickle-cell sufferers to receive the drug. Placebos were given to another 150 sickle-cellsufferers. Great care was used to ensure that the 300 participants did not know if their pill contained the drug. Atthe end of the treatment period, the researchers counted the number of episodes of pain reported by eachsubject.

Q:Which of the following principles was notused in this study?

A. Control

B. Blinding

C. Randomization

D. Blocking

E. None of the above