In a double blind clinical drug trial:

Ans. is 'c' i.e. The patients do not know which treatment they are receivingRef. Park 20th/e, p 79, 18th/e, p. 77 (17th/e p 73)Blinding was introduced to prevent bias during randomized controlled trial.Single Blind TrialThe trial is so planned that the participant is not aware whether he/she belongs to the study group or the control groupDouble Blind TrialThe trial is so planned that neither the doctor nor the participant is aware of the group allocation and the treatment receivedTriple Blind TrialThis goes one step further. The participant, the investigator and the person analysing the data are all "blind."Ideally, of course, triple blinding should be used, but the double blinding is the most frequently used method when a blind trial is conducted.Remember, when the outcome such as death is being measured, blinding is not so essential.