1. Single Blind TrialThis trial is planned in such a way that the participants (patients or study population) are not aware whether they belong to study group or control group.
2. Double Blind Trial:
This trial is so planned that neither the doctor nor the participant is aware of the group allocation and the treatment received.
3. Triple Blind Trial:
This is one step further. The participant, the doctor and the person analysing the data are all blind. Ideally triple blinding should be used but the double blinding is the most commonly used method. In some cases blinding is not so important for example when an outcome such as death is being measured.