A retrospective analysis or retrospective study is a research method that is used when the outcome of an event is already known. For example, medical researchers might study the records of patients who suffered from a particular disease to determine what factors may have led to their illness or death.
Retrospective Analysis Uses
A retrospective analysis is the opposite of a prospective study, which is where investigators design the study before the subjects develop a particular disease. Retrospective studies are often used in medicine, but they are also used by ecologists, historians and criminologists, as well as researchers in many other disciplines.
Advantages and Disadvantages
According to Dr. Dean Hess, assistant director of respiratory care at Massachusetts General Hospital, some researchers call retrospective studies a "quick and dirty" method of answering a question. The data has already been collected and the subjects have been identified, so studies can be conducted quickly and economically. However, the data is secondary and researchers do not have any control over how the information was collected, so the available documentation may be incomplete or biased.
A retrospective analysis should not be conducted if an original study is an option; retrospective analyses are useful as pilot studies before planning a prospective study. They can be used to help formulate the hypothesis, focus the questions and identify any major issues before a prospective study begins.