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Case-Control Study A case-control study is a retrospective study that looks back in time to find the relative risk between a specific exposure (e.g. The goal is figure out the relationship between risk factors and disease or outcome and estimate the odds of an individual getting a disease or experiencing an event. A control group of people who do not have the disease or who did not experience the event is used for comparison.Case–control studies are often used to identify factors that may contribute to a medical condition by comparing subjects who have that condition/disease (the "cases") with patients who do not have the condition/disease but are otherwise similar (the "controls").
Numbers of cases and controls do not have to be equal.
In many situations, it is much easier to recruit controls than to find cases.
Increasing the number of controls above the number of cases, up to a ratio of about 4 to 1, may be a cost-effective way to improve the study.
A prospective study watches for outcomes, such as the development of a disease, during the study period and relates this to other factors such as suspected risk or protection factor(s).
All efforts should be made to avoid sources of bias such as the loss of individuals to follow up during the study.
Prospective studies usually have fewer potential sources of bias and confounding than retrospective studies.Most sources of error due to confounding and bias are more common in retrospective studies than in prospective studies.For this reason, retrospective investigations are often criticised.With Chegg Study, you can get step-by-step solutions to your questions from an expert in the field. - Includes many concepts such as sample size, hypothesis tests, or logistic regression, explained by Stephanie Glen, founder of Statistics How To. A case–control study (also known as case–referent study) is a type of observational study in which two existing groups differing in outcome are identified and compared on the basis of some supposed causal attribute.The potential relationship of a suspected risk factor or an attribute to the disease is examined by comparing the diseased and nondiseased subjects with regard to how frequently the factor or attribute is present (or, if quantitative, the levels of the attribute) in each of the groups (diseased and nondiseased)." For example, in a study trying to show that people who smoke (the attribute) are more likely to be diagnosed with lung cancer (the outcome), the cases would be persons with lung cancer, the controls would be persons without lung cancer (not necessarily healthy), and some of each group would be smokers.If a larger proportion of the cases smoke than the controls, that suggests, but does not conclusively show, that the hypothesis is valid.One should take special care to avoid sources of bias and confounding  in retrospective studies.Case–control studies are a relatively inexpensive and frequently used type of epidemiological study that can be carried out by small teams or individual researchers in single facilities in a way that more structured experimental studies often cannot be.We only get odds ratio from a case–control study, which is an inferior measure of strength of association as compared to relative risk.The case–control is a type of epidemiological observational study.