What is a defining feature of a double-blind study?

A double-blind study is characterized by the fact that neither the participants nor the researchers know which individuals belong to which group (e.g., the treatment group or the control group). This design is critical in experimental research as it helps to mitigate biases that can affect the results. When both parties are unaware of the group assignments, it reduces the potential for expectations or preconceptions to influence outcomes, either during the administration of the treatment or while collecting and interpreting data.

This feature enhances the validity of the study by ensuring that any changes observed can more confidently be attributed to the independent variable being tested, rather than to biases introduced through knowledge of group assignment. It is a fundamental aspect of rigorous experimental design, particularly in areas such as clinical trials, where the influence of placebo effects and subjective interpretations can significantly impact the results.