What is blinding?
blinding is The concealment of group assignment (to either the treatment or control group) from the knowledge of participants and/or investigators in a clinical trial. Blinding eliminates the possibility that knowledge of assignment may affect individual response to treatment or investigator behaviours that may affect outcomes. Blinding is not always practical (e.g. when comparing surgery to drug treatment) but it should be used whenever it is possible and compatible with optimal care. There are various kinds of blinding:
source: A GLOSSARY OF TERMS FOR COMMUNITY HEALTH CARE AND SERVICES FOR OLDER PERSONS. World Health Organization, 2004.