## **Core Concept**
The risk ratio, also known as the relative risk (RR), is a measure used in epidemiology to compare the risk of a certain event (such as developing a disease) occurring in one group with the risk of the same event occurring in another group. It is calculated as the ratio of the probability of an event occurring in the exposed group versus the non-exposed group.

## **Why the Correct Answer is Right**
To calculate the risk ratio (RR) of developing hypertension in smokers compared to non-smokers, we first need to determine the risk of developing hypertension in each group. The risk in smokers is 60/200 = 0.3, and the risk in non-smokers is 30/600 = 0.05. The risk ratio (RR) is then calculated as the risk in the exposed group (smokers) divided by the risk in the non-exposed group (non-smokers): RR = 0.3 / 0.05 = 6. This means that smokers are 6 times more likely to develop hypertension than non-smokers.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because the calculation does not match the provided numbers and does not reflect the correct formula for risk ratio.
- **Option B:** This option is incorrect because, similar to option A, it does not correctly represent the risk ratio calculation based on the given data.
- **Option D:** This option is incorrect because it also does not accurately reflect the calculation of the risk ratio based on the provided study data.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that a risk ratio (RR) of 1 indicates no difference in risk between the two groups. An RR greater than 1 indicates an increased risk in the exposed group, while an RR less than 1 indicates a decreased risk. In this case, an RR of 6 indicates a significantly increased risk of developing hypertension in smokers compared to non-smokers.

## **Correct Answer:** .