In a double-blind study, both the participant (subject) and the investigator (or clinical staff administering the treatment) are blinded. This approach minimizes bias in treatment administration and outcome assessment. Blinding the subject ensures that their responses are not influenced by their knowledge of the treatment they are receiving.

According to GCP guidelines, double-blinding is essential to eliminate both participant and investigator bias, ensuring objective trial results.

"Double-blind studies ensure that neither the participant nor the investigator knows which intervention is being administered, thereby minimizing bias."

Objectives:

Maintain the integrity of the study by preventing bias.

Enhance the validity of trial outcomes.