Sensitivity refers to how well a test identifies every member of a defined group.

• A. The rate of false positives
• B. The proportion of true negatives
• C. The overall test efficiency
• D. To how well a test identifies every member of a defined group

Answer: (D)

Sensitivity is the test’s ability to correctly identify people who truly have the condition. It tells you what fraction of those in the defined group with the condition are detected as positive by the test. When sensitivity is high, there are few false negatives—the test doesn’t miss many real cases.

That idea matches the description “to how well a test identifies every member of a defined group,” which is why it’s the best choice.

The other options describe different ideas: the rate of false positives relates to how often healthy people are labeled positive; the proportion of true negatives is the true negative rate (specificity); and overall test efficiency isn’t a precise metric for catching true positives.