Use the Following Information for Questions

Multiple Choice

Use the following information for questions:
Sickle-cell disease is a painful disorder of the red blood cells that in the United States affects mostly blacks. To investigate whether drug A can reduce the pain associated with sickle-cell disease, a study by the National Institutes of Health randomly assigned 150 sickle-cell sufferers to receive the drug. Placebos were given to another 150 sickle-cell sufferers. Great care was used to ensure that the 300 participants did not know if their pill contained the drug. At the end of the treatment period, the researchers counted the number of episodes of pain reported by each subject.
-What type of study is this?

A) Observational study
B) Randomized experiment
C) Matched pairs study
D) Repeated measures study