Learning Objective:
Understand and apply the formula for Specificity, which measures the ability of a test to correctly identify those without the disease (true negatives).

Formula:

Explanation:

• TN (True Negatives): Individuals who do not have the disease and test negative.
• FP (False Positives): Individuals who do not have the disease but test positive.
• Specificity reflects how good a test is at avoiding false positives.

Interpretation:

• High specificity → few false positives → good for confirmatory tests (rule in disease).
• Use the mnemonic “SpPin” — a highly SPecific test, when Positive, rules in the disease.

Example:

If a test correctly identifies 80 out of 100 non-diseased patients:
,

✅ Answer: Specificity = 80%