Blinding in Clinical Trials
7. Double Blind
A clinical trial design in which neither the participants nor investigators know which participants are receiving the experimental medicine and which are receiving a placebo (or comparator therapy). Double-blind trials are thought to produce objective results, since the expectations of the investigator and the participant do not affect the outcome. Also called double-masked trial.
- Considered best-controlled trial design.
- Decreased chance of preconceived notions or physical cues (e.g. the placebo effect, observer bias, experimenter's bias) to distort the results.
- The key that identifies the participants and which group they belonged to is kept by a third party, and is not revealed to the researchers until the study is over.
- Should be used whenever possible.