In a double-blinded study, who is unaware of treatment assignment?

In a double-blinded study, who is unaware of treatment assignment?

• A. Both subjects and investigators know
• B. Only subjects know
• C. Only investigators know
• D. Neither subjects nor investigators know

Answer: (D)

In a double-blinded study, neither the people receiving the treatment nor the clinicians or researchers administering it and assessing outcomes know which treatment was given. This prevents bias from both sides: patients’ expectations won’t color their reported symptoms, and investigators’ assessments won’t be swayed by knowledge of the treatment. That’s why this setup yields more objective results. If both groups knew, that would be unblinded; if only the patients knew, or only the investigators knew, that would be single-blind. In this question, the scenario described is that neither side knows, which is the hallmark of a double-blind design.

In a double-blinded study, neither the people receiving the treatment nor the clinicians or researchers administering it and assessing outcomes know which treatment was given. This prevents bias from both sides: patients’ expectations won’t color their reported symptoms, and investigators’ assessments won’t be swayed by knowledge of the treatment. That’s why this setup yields more objective results.

If both groups knew, that would be unblinded; if only the patients knew, or only the investigators knew, that would be single-blind. In this question, the scenario described is that neither side knows, which is the hallmark of a double-blind design.