A word about blinded studies.

When possible, medical researchers like to blind, or mask, their clinical trials. In a single-blinded trial, participants do not know whether they are in the intervention group or the control group until the trial ends. In a double-blinded trial, neither investigators nor participants know which group a participant is assigned to until the trial's conclusion.

Blinding is another way of reducing bias that may distort a study's results. For example, investigators may behave differently toward participants whom they know are receiving the experimental intervention.

However, blinding is not always feasible. In a trial comparing surgery with chemotherapy, for example, blinding would be impossible -- both doctors and participants would know which intervention was being applied.

Cancer prevention clinical trials are sometimes blinded, but cancer treatment trials rarely are.

Back to Top

< Previous Section  |  Next Section >