The 1971 Stanford Prison Experiment, though unconventional, can be called a true experiment. Designed to test the psychology of the prison environment, the experiment simulated a prison in which subjects were randomly assigned the role of either "prisoner" or "guard." The simulation produced dramatic outcomes; guards quickly became controlling and even sadistic, and prisoners experienced psyhological stress, depression, and even physical illness. The intensity of the situation forced researchers to ended the study prematurely, but its construction as a true experiment still allowed researchers to assess a relationship between variables and gain valuable insight into the power of assigned roles.
A true sociological experiment can be defined as an experiment in which subjects are assigned randomly to an experimental group and one or more comparison groups, with outcomes measured over time (Schlutt I-20). Conventionally, an experiment's comparison group is a control group (a group recieving no treatment); however, a comparison group may also be a group of subjects recieving a treatment or variation of the independent variable differing from that of the experimental group (Schlutt 176-178). This is the case with the Stanford Prison Experiment: both groups (the guards and the prisoners) recieved treatment in varying degrees, and there was no control group. .
.
The treatment given to Stanford Prison Experiment's subjects (the independent variable) was the assignment of power. Those assigned to be guards were given a great deal of power; they made up the prison rules and were allowed to use whatever means they deemed necessary (within reason) to enforce these rules and maintain order. Prisoners, on the other hand, were chained together, locked in tiny cells at all times, and forced to submit to the will of the guards. Researchers aimed to discover the effect of these different power roles on the behavior, attitude, and mental state of the subjects (the dependent variable).