Final answer:
A double-blind study is a scientific experiment in which both the subjects and the researchers are unaware of which subjects are in which group. It is used to control for biases and prevent the placebo effect in clinical trials of medical treatments.
Step-by-step explanation:
A study in which both the subjects and the researchers do not know which subjects are in which group is known as a double-blind study. In a double-blind experiment, both the subjects and the researchers involved are blinded to group assignments to control for biases and prevent the placebo effect.
This type of experiment is considered the gold standard for clinical trials of medical treatments, vaccines, and therapeutic drugs.