ABSTRACT
A true experiment will divide participants into the control and experimental groups randomly. Without random assignment to groups, a study does not meet the criteria of an experiment. Experiments are generally considered a more definitive and rigorous form of evidence than nonexperimental studies because they answer more directly whether an intervention can help to explain an outcome, while controlling for other explanations. Some common types of nonexperimental studies are surveys, polls, interviews, and observation. These methods may ask participants about their attitudes, beliefs, and behaviors instead of observing them. Consumers of research cannot distinguish between nonexperimental and experimental studies based on the type of measure used. Measures such as paper-and-pencil tests, interview schedules, and personality scales are used in both types of studies. The fundamental difference between experimental and nonexperimental study designs rests in the use of a manipulation or treatment.
