Double-Blind Procedure (also known as Double Blind Control) This is one type of experimental procedure in which both the patient and the staff are ignorant (blind) as to the condition (or group) that the participant is in. This would make it impossible for the participant or researcher to know if the participant is receiving the treatment (for example a drug) or a placebo. This type of design is commonly used in drug evaluation studies, and is used to prevent the researchers from acting differently to people in one group, or from giving the participant any information that could make them act and/or behave unnaturally.