double-blinded

Definition of double-blind study
National Cancer Institute

double-blind study

(DUH-bul-blind STUH-dee)
A type of clinical trial in which neither the participants nor the researcher knows which treatment or intervention participants are receiving until the clinical trial is over. This makes results of the study less likely to be biased. This means that the results are less likely to be affected by factors that are not related to the treatment or intervention being tested.

Source: NCI Dictionary of Cancer Terms