Doppelblinddesign

Doppelblinddesign, commonly called a double-blind design in English, is an experimental setup in which neither the participants nor the researchers who interact with them know which treatment each participant receives. The aim is to prevent biases that could influence treatment administration, participant behavior, or outcome assessment, thereby increasing the internal validity of the trial or study.

Implementation typically involves random assignment to treatment groups, allocation concealment so the next assignment cannot be predicted, and the use of indistinguishable interventions or placebos. In pharmaceutical trials, for example, an active drug and a placebo are prepared to appear identical, ensuring that neither the patient nor the clinician knows which is being administered. Blinding can be extended to outcome assessors and data analysts, creating a higher level of concealment sometimes referred to as a triple-blind design.

Variants and related approaches include the double-dummy design, which allows comparison of two active treatments with different forms (for instance, pills and injections) by giving each participant both a placebo and an active form as needed. If full blinding is not feasible, researchers may employ partial blinding or single-blind designs, where only one party remains unaware of the allocation.

Applications of Doppelblinddesign are most common in clinical trials, especially pharmaceutical research, but are also used in psychology, behavioral studies, and other areas where objective assessment is important. While it can reduce bias, double-blind designs are not always possible or ethical, and blinding integrity must be carefully monitored to prevent unblinding through side effects, procedural clues, or other indicators.