What is double-blind research and its benefit?

• A. In double-blind research, both participants and researchers know group assignments.
• B. In double-blind research, only participants do not know their group.
• C. In double-blind research, neither participants nor researchers know who is in the experimental or control group, reducing bias and demand characteristics.
• D. In double-blind research, the data are collected by a computer algorithm.

Answer: (D)

Double-blind research is a study design where neither the participants nor the researchers who interact with them know who is receiving the active treatment and who is in the comparison group. The key benefit is reducing bias that can come from expectations. If researchers know which participants are getting the treatment, they might unconsciously treat them differently or record outcomes in a biased way. If participants know their group, their responses can be influenced by expectations or placebo effects, which is called demand characteristics. By keeping both sides unaware, the study yields more trustworthy evidence about the true effect of the intervention.

For comparison, having only participants unaware is a single-blind approach, and knowing group assignments by both sides would introduce bias. The idea of data collection by a computer doesn't define double-blind; it’s about who knows the group assignments, not who collects the data.