title: Significance of retrospective studies.
abstract: Examples of retrospective studies are presented to demonstrate some facets of such studies, both good and bad, pointing out the need for good controls. Also important are a clear idea of the question to be answered, and careful planning around that answer as the study progresses.
mesh_terms: D000230:Adenocarcinoma / Q000139:chemically induced; D004967:Estrogens; D005260:Female; D006323:Heart Arrest / Q000209:etiology; D006801:Humans; D007603:Jurisprudence; D008175:Lung Neoplasms / Q000209:etiology; D008297:Male; D010383:Pellagra / Q000209:etiology; D012189:Retrospective Studies; D012907:Smoking / Q000150:complications; D011795:Surveys and Questionnaires; D014625:Vaginal Neoplasms / Q000139:chemically induced
chemical_list: D004967:Estrogens