Case-control studies are an observational study method that selects people with a disease and those without a disease to investigate their exposure to a risk factor and its degree respectively, so as to determine whether the exposure risk factor is related to a disease and the degree of association.

Drawbacks of Case-Control: (Tobacco case as an example) -Retrospective: We know the subject has cancer, and in that context we have to go back and figure out why -Reversed logic of probability: What these data tell us is the probability that cancer patients are smokers, not the probability that smokers get cancer. For those who want to know if they should smoke, the probability of cancer in smokers is the probability they really care about -Selection Bias: Hospitalized cancer patients (aka those on record as having cancer) may not be representative of the population at large or even the smoking population at large. -Recall Bias: The interviewees themselves already know they had cancer, so this can impact their subjective recollection of events.