**Core Concept**
Population attributable risk (PAR) is a measure used in epidemiology to quantify the proportion of disease incidence in a population that can be attributed to a specific risk factor. It is an important concept in understanding the impact of risk factors on disease prevalence.

**Why the Correct Answer is Right**
The correct answer is the difference between the incidence of the disease in the exposed population and the incidence in the non-exposed population. This is calculated using the formula: PAR = (Risk in exposed - Risk in non-exposed) / Risk in exposed. This measure helps to quantify the proportion of disease incidence that can be attributed to a specific risk factor, allowing for a better understanding of the impact of that risk factor on disease prevalence.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe the formula for calculating population attributable risk. The correct formula involves comparing the incidence of disease in exposed and non-exposed populations.
**Option B:** This option is incorrect because it is not a valid measure of population attributable risk. The correct measure involves comparing incidence rates, not prevalence rates.
**Option C:** This option is incorrect because it is a measure of relative risk, not population attributable risk. While relative risk can provide information about the strength of association between a risk factor and disease, it does not quantify the proportion of disease incidence that can be attributed to that risk factor.

**Clinical Pearl / High-Yield Fact**
Population attributable risk is an important measure in epidemiology, as it helps to quantify the impact of risk factors on disease prevalence. It is often used in conjunction with other measures, such as relative risk and odds ratio, to provide a more complete understanding of the relationship between risk factors and disease.

**Correct Answer:**
D. The incidence of the disease in the exposed population minus the incidence of the disease in the non-exposed population.