Incidence of disease among exposed divided that of non exposed is equal to –
**Core Concept**
The question is testing the understanding of the **Attributable Risk**, a measure used in epidemiology to assess the association between a risk factor and a disease. Attributable Risk is a key concept in evaluating the burden of disease and the effectiveness of interventions.
**Why the Correct Answer is Right**
The formula for Attributable Risk is (Incidence among exposed - Incidence among non-exposed) / Incidence among exposed. This ratio represents the proportion of disease incidence that can be attributed to the exposure. In other words, it measures the excess risk of disease among the exposed population compared to the non-exposed population.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately represent the formula for Attributable Risk. The correct formula involves subtracting the incidence among non-exposed from the incidence among exposed, and then dividing by the incidence among exposed.
**Option B:** This option is incorrect because it represents the **Relative Risk**, which is the ratio of the incidence among exposed to the incidence among non-exposed. It does not take into account the excess risk among the exposed population.
**Option C:** This option is incorrect because it represents the **Odds Ratio**, which is a measure of association between a risk factor and a disease, but it is not directly related to the Attributable Risk.
**Option D:** This option is incorrect because it is incomplete and does not provide a clear formula or calculation.
**Clinical Pearl / High-Yield Fact**
Remember that Attributable Risk is a useful measure for evaluating the effectiveness of interventions and the burden of disease, but it has limitations, such as being sensitive to the prevalence of the disease and the exposure. Always consider the context and limitations when interpreting Attributable Risk.
**Correct Answer: A. (Incidence among exposed - Incidence among non-exposed) / Incidence among exposed.**