Question

Describe the following for a given test: 
Specificity. 
 

Hint:

A highly specific test is useful for confirming the diagnosis (i.e., a positive result confirms the disease).

Answer 1

Step 1: Defining Specificity.
Specificity, also known as the true negative rate, refers to the ability of a test to correctly identify those without the disease or condition. It is the proportion of true negatives among all those who do not have the disease.

Step 2: Formula for Specificity.
\[ \text{Specificity} = \frac{\text{True Negatives}}{\text{True Negatives + False Positives}} \] Where:
- True Negatives (TN): The number of people who do not have the disease and test negative.
- False Positives (FP): The number of people who do not have the disease but test positive.

Step 3: Conclusion.
A high specificity means that the test is good at identifying those without the disease and has a low rate of false positives. It is crucial in confirmatory tests to ensure that individuals who are identified as negative are truly disease-free.