![]() This type of study can also be used to investigate the effectiveness of various safety practices. For example, retrospective studies into military veterans with cancer were able to provide information into how exposure to the toxic herbicide Agent Orange was causally linked to increased incidence of cancer amongst exposed U.S. Many important studies into occupational hazards have been retrospective studies. This makes them useful for conducting research into conditions that would be too resource-intensive to study using prospective methods. One benefit is that they allow researchers to select the desired number of people with the condition they are studying, which means that the overall number of people in the study can be significantly less than in a prospective study, and are quicker to complete. Retrospective studies have both benefits and drawbacks. For example, a retrospective study of breast cancer patients would involve comparing a group of people with breast cancer to a similar group of people without breast cancer, while a prospective study would involve recruiting a single group of people without breast cancer and monitoring them for an extended period in order to try and discover insights into why some of them developed breast cancer during the study. These studies need to look at very large samples to ensure that any attributional losses can be absorbed by the statistics.Retrospective studies are so-named because they involve looking backwards at the histories of the people being studied, rather than monitoring a group of people over an extended period (a prospective study). The ambidirectional study shares one major drawback with the prospective study, in that it is impossible to guarantee that any data can be followed up, as participants may decline to participate or die prematurely. This gives the most accurate results, but is an extremely arduous undertaking, costing time and a great deal of money. ![]() The researcher studies and analyzes the previous history of the cohorts and then continues the research in a prospective manner. The ambidirectional cohort study is the ultimate method, combining retrospective and prospective aspects. The prospective cohort study is a great way to study long-term trends, allowing the researcher to measure any potential confounding variables, but the potential cost of error is high, so pilot studies are often used to ensure that the study runs smoothly. Some studies have been running for decades, but are generating excellent data about underlying trends in a population. ![]() ![]() They are preferable to a retrospective study, but are expensive and usually require a long period of time to generate useful results, so are very expensive and difficult. It is also possible to subgroup and try to control variables, such as weight, occupation type or social status. TYPES OF RETROSPECTIVE STUDIES FREETo maintain validity, all of the subjects must be initially free of the condition tested for.įor example, an investigation, over time, into the effects of smoking upon lung cancer must ensure that all of the subjects are free of the disease. ![]() In a prospective cohort study, the effects of a certain variable are plotted over time, and the study becomes an ongoing process. ![]()
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