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Biostatistics & Research · single question

What does 'specificity' measure for a diagnostic test?

  1. The test's ability to correctly identify those WITHOUT the disease: true negatives ÷
  2. The test's ability to correctly identify those WITH the disease
  3. The probability that results occurred by chance
  4. The proportion of a population with a disease at a point in time
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Correct answer: A. The test's ability to correctly identify those WITHOUT the disease: true negatives ÷

Specificity = true negatives ÷ (true negatives + false positives) — it measures how well a test avoids false alarms in people who don't actually have the disease. Sensitivity, by contrast, measures true positives ÷ (true positives + false negatives), reflecting how well a test catches people who DO have the disease.

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