In a double-blind clinical drug trial:
The double blind trial is so planned that neither the doctor nor the paicipant is aware of the group allocation and the treatment received. Ref: 25th edition, Park's Textbook of Preventive and Social Medicine, Page no. 91
Each patient receives a placebo
Each patient receives both (double) treatments
The patients do not know which treatment they are receiving
The patients do not know that they are in a drug trial
Epidemiology