The relative risk of a disease measures the –
**Core Concept**
Relative risk is a statistical measure used in epidemiology to compare the likelihood of a specific outcome or disease in one group to another group. It is a ratio of the probability of an event occurring in the exposed group versus the non-exposed group.
**Why the Correct Answer is Right**
Relative risk is calculated as the incidence rate of the disease in the exposed group divided by the incidence rate of the disease in the non-exposed group. This measure is useful for determining the strength of association between a potential risk factor and a disease. It helps researchers and clinicians understand the potential impact of a particular risk factor on disease development. In essence, relative risk provides a quantitative estimate of the increased risk of disease in the exposed group compared to the non-exposed group.
**Why Each Wrong Option is Incorrect**
**Option A:** Absolute risk is a measure of the total risk of a disease in a population, not a comparison between two groups.
**Option B:** Odds ratio is a measure of association between an exposure and an outcome, but it is not a direct measure of risk.
**Option C:** Number needed to treat is a measure of the number of patients that need to be treated to prevent one adverse outcome, not a measure of risk.
**Clinical Pearl / High-Yield Fact**
When interpreting relative risk, it's essential to consider the baseline risk of the disease in the non-exposed group. A small relative risk can still have a significant impact on public health if the baseline risk is high.
**Correct Answer: B. Odds ratio.