NCERT Example 18 - Probability
Question: HIV test reliability: of people having HIV, 90% test positive; of people free of HIV, 99% test negative (1% false positive). If 0.1% of the population has HIV, find the probability that a person has HIV given a positive test.
Answer: 90/1089 (≈ 0.0826).
Full step-by-step NCERT solution with diagrams on Something by Zero.