Incidence of disease in exposed divided by incidence among non-exposed is –
**Core Concept**
The question is testing the understanding of the concept of relative risk, which is a measure used in epidemiology to compare the risk of a disease or outcome between two groups: exposed and non-exposed. It is calculated as the ratio of the incidence of the disease in the exposed group to the incidence of the disease in the non-exposed group.
**Why the Correct Answer is Right**
Relative risk is a crucial measure in epidemiology as it helps to quantify the association between a risk factor and a disease. It is calculated by dividing the incidence of the disease in the exposed group by the incidence of the disease in the non-exposed group. This allows researchers to determine the strength of the association between the risk factor and the disease. For example, if the relative risk is 2, it means that the incidence of the disease in the exposed group is twice that of the non-exposed group.
**Why Each Wrong Option is Incorrect**
**Option A:** This is incorrect because it describes the concept of odds ratio, which is a measure of association between an exposure and an outcome in case-control studies.
**Option B:** This is incorrect because it describes the concept of attributable risk, which is the difference in incidence between exposed and non-exposed groups.
**Option C:** This is incorrect because it is a description of the concept of risk difference, which is the absolute difference in risk between exposed and non-exposed groups.
**Clinical Pearl / High-Yield Fact**
Remember that relative risk is a measure of the strength of association between a risk factor and a disease, and it is calculated by dividing the incidence of the disease in the exposed group by the incidence of the disease in the non-exposed group. This concept is crucial in epidemiology and is used to inform public health policy and clinical practice.
**Correct Answer: A. Relative Risk**