In a double-blind experiment, participants AND researchers are unaware which is the treatment group and which is the control group.

• A. Double-blind
• B. Single-blind
• C. Open-label
• D. Triple-blind

Answer: (A)

The concept being tested is blinding to prevent bias in how results are observed and interpreted. In a double-blind setup, neither the participants nor the researchers know who is receiving the treatment versus the control. This keeps expectations from shaping reporting, behavior, or assessment of outcomes, so the results reflect the treatment itself rather than beliefs about who received it.

If only the participants were unaware, with researchers knowing, that would be a single-blind design, which leaves room for observer or investigator bias. If everyone knows who’s in which group, that’s open-label, where no blinding occurs. A triple-blind design is even more restrictive, typically keeping data analysts unaware as well, but the scenario described fits the standard double-blind approach.