Why are double blind trials used?

• A. To prevent researcher bias and placebo effects.
• B. To speed up the study.
• C. To increase sample size.
• D. To reduce funding costs.

Answer: (A)

Double blind trials are designed to keep bias out of the results by hiding who receives the actual treatment from both participants and those assessing the outcomes. When participants don’t know what they’re getting, their expectations can influence how they report symptoms or improvements—the placebo effect. When researchers don’t know which participants received the active treatment, they’re less likely to unconsciously rate or record outcomes in a biased way or treat groups differently. By removing these sources of influence, the observed differences are more likely to reflect the true effect of the treatment, improving the study’s internal validity. The other ideas—speeding up the study, increasing the number of participants, or cutting costs—are not the reason for blinding and could even be compromised by it.