Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025
Definition
A placebo is an inactive substance or treatment given to a group of participants in an experiment to compare its effects with those of an active treatment. The purpose is to control for the psychological effects of receiving a treatment.
5 Must Know Facts For Your Next Test
Placebos are used as controls in experiments to help determine the actual effectiveness of the experimental treatment.
The placebo effect occurs when participants experience changes simply because they believe they are receiving a treatment.
Placebo groups help researchers isolate the physiological effects of the real treatment from psychological or other effects.
Blinding is often used alongside placebos to prevent bias; participants and sometimes researchers do not know who receives the placebo.
Ethical considerations must be taken into account when using placebos, especially in medical research.
A method used in experiments where information about which participants receive specific treatments is withheld to prevent bias.
Double-Blind Study: An experimental design where neither the participants nor the researchers know who belongs to the control group and who belongs to the experimental group, reducing bias.