In a population of 1000 people, 100 have a disease. A screening test is positive in 80 of the 100 people with the disease and in 45 of the 900 people without it. What is the sensitivity of the test?
Answer and explanation
Correct answer: B. 80 percent
- Step 1: Sensitivity is the proportion of people with the disease who test positive: true positives divided by all with disease. Step 2. True positives are 80 of the 100 people with disease, so sensitivity is 80/100 = 80 percent. Answer: 80 percent. Why not the others: 64 percent is the positive predictive value (80 of 125 positives). 95 percent is the specificity. 55 percent is not given by any calculation.
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