Double-blind research design is defined as

• A. A research study in which both the researcher and the participants are unaware of the predicted outcome
• B. A research study in which only the participants are unaware of the predicted outcome
• C. A research study in which only the researchers are unaware of the predicted outcome
• D. An uncontrolled study with no blinding

Answer: (A)

Double-blind means neither the participant nor the investigator who interacts with them knows which treatment the participant is receiving or what outcome is expected. This setup prevents bias from both sides: participants can’t be influenced by expectations about the treatment, and researchers can’t unconsciously influence assessments or data collection. A placebo is typically used to make the treatment and control look identical, with random assignment to groups. This contrasts with single-blind designs, where only one party is unaware, and with studies that have no blinding at all, which are more susceptible to bias. The goal is to obtain a more accurate estimate of the treatment effect, especially for subjective outcomes.