In case control studies
.case control studies are retrrspective studies,that proceeds from effect to cause.it requires two study groups,namely cases and controls.both exposure and outcome has occurred at the time of study.they are basically comparison studies,four basic steps of this incudes, selection of cases and controls matching measurement of exposure analysis and interpretation,from a case control study we can derive odd&;s ratio that is a measure of association between risk factor and outcome.it is closely related to relative risk. ref:park&;s textbook,ed22,pg no 70
Many patients are needed
Incidence can be calculated
Cause to effect is preceded
Odd ratio can be calculated
Epidemiology