Sickle-cell disease is a painful disorder of the red blood cells. To investigate whether a drug can reduce pain associated with sickle-cell disease, a study by NIH gave a placebo to 150 sufferers and gave a new drug to another 150. Doctors knew which treatment each participant received. The number of episodes of pain reported by each subject was recorded. 2 pts. a) Is this an experiment or an observational study? Explain. 1 pt. b) Explain how the 300 subjects could have randomly been divided into 2 groups. 2 pts. d) Explain how this is a single-blind study. 1 pt. c) What is the response variable? Edit View Insert Format Took Table 12pt v Paragraph B J U A & T