A rare condition affects 1 person in 200. A test has sensitivity 0.98, so it is positive for 98% of people with the condition. Its specificity is 0.95, so it is negative for 95% of people without the condition.
Find the probability that a randomly selected person receives a positive result.
Given a positive result, find the probability that the person has the condition.
Explain why the answer to part (b) is much less than 0.98.
164 exam-style questions on WJEC A Level Maths 4.1 Probability (A-level only), covering 4.1.1 Probability (A-level only), 4.1.2 Probability (A-level only), and 4.1.3 Probability (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.