Case-control study: The traditional case-control study is the common research design in the epidemiology where the exposures to risk factors for cases (individuals getting the disease) are compared to the exposures for controls (individuals not getting affected by the disease). The design is retrospective in the sense which a sample of controls is sampled from the subjects who are disease free at the end of the observation time period. The primary benefit of this design is that exposure information is required to be gathered for only a small proportion of the cohort members, thereby considerably reducing data collection costs. The major disadvantage is the potential for recall bias.