1. The problem is to find the probability that a person has the disease given a positive test result, using the sensitivity, specificity, and prevalence.
2. We use Bayes' theorem: $$P(D|T) = \frac{P(T|D) \times P(D)}{P(T|D) \times P(D) + P(T|\neg D) \times P(\neg D)}$$ where:
- $P(D)$ is the prevalence (probability of disease) = 0.02
- $P(\neg D)$ is the probability of no disease = 1 - 0.02 = 0.98
- $P(T|D)$ is sensitivity = 0.95
- $P(T|\neg D)$ is false positive rate = 1 - specificity = 1 - 0.90 = 0.10
3. Substitute values:
$$P(D|T) = \frac{0.95 \times 0.02}{0.95 \times 0.02 + 0.10 \times 0.98}$$
4. Calculate numerator and denominator:
$$= \frac{0.019}{0.019 + 0.098} = \frac{0.019}{0.117}$$
5. Simplify fraction:
$$= \frac{\cancel{0.019}}{\cancel{0.117}} = 0.1624$$ (approx.)
6. So, the probability that a person has the disease given a positive test is approximately 16.24%.
This matches the answer option approx. 16%.
Bayes Probability Ec73Ca
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