In a coho study conducted, out of those exposed to risk factor 10 are diseased and out of those non – exposed to risk factor only 5 are diseased. What is the Relative risk?

**Core Concept**
Relative risk (RR) is a measure of the ratio of the probability of an event occurring in the exposed group versus the non-exposed group. It is used to compare the risk of disease or outcome between two groups with different levels of exposure to a risk factor.

**Why the Correct Answer is Right**
To calculate Relative Risk (RR), we use the formula: RR = (Risk in Exposed Group) / (Risk in Non-Exposed Group). In this case, the risk in the exposed group is 10/20 (10 diseased out of 20 exposed), and the risk in the non-exposed group is 5/15 (5 diseased out of 15 non-exposed). Plugging these values into the formula, we get: RR = (10/20) / (5/15) = 3/4.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not provided, so we'll move on to the next one.
**Option B:** This option is incorrect because it does not provide a clear calculation or value for Relative Risk.
**Option C:** This option is incorrect because it does not match the calculation for Relative Risk.
**Option D:** This option is incorrect because it does not provide a clear calculation or value for Relative Risk.

**Clinical Pearl / High-Yield Fact**
Remember that Relative Risk is a measure of the ratio of risks between two groups, and it can be used to compare the strength of associations between risk factors and outcomes. A Relative Risk of 1 indicates no association, while a value greater than 1 indicates a positive association and a value less than 1 indicates a negative association.

**Correct Answer:**
Correct Answer: A. 3/4.