A social experiment is a research project conducted with human subjects in the real world. It typically investigates the effects of a policy intervention by randomly assigning individuals, families, businesses, classrooms, or other units to different treatments or to a controlled condition that represents the status quo. The qualifier "social" distinguishes a policy experiment from a "clinical" experiment, typically a medical intervention within the subject's body, and also from a laboratory experiment, such as a university psychology faculty might conduct under completely controlled conditions. In a social experiment, randomization to assigned treatment is the only element in the subject's environment that the researchers control. All other elements remain exactly what they were.