Natural Experiments

A natural experiment is a naturally occurring instance of observable phenomena that approach or duplicate a scientific experiment. Notable events such as elections, disasters, and policy implementation often provide the basis for natural experiments that permit examination of alternate reactions and explanations for them. Such occurrences may lend themselves to the examination of reactions of subgroups or straightforward comparisons of data collected before and after an event. The 2000 presidential election in the United States and the events of 9/11 are events that have spawned many natural experiments. An example of a natural experiment occurred in Helena, Montana, while a public smoking ban was in effect. Helena is geographically isolated and served by only one hospital. Data collected by the hospital indicate that the rate ...