A screening test is used for a medical condition. It is known that 2% of the people who are screened have the condition.
If a person has the condition, the probability that the test is positive is 0.95.
If a person does not have the condition, the probability that the test is positive is 0.04.
Find the probability that a randomly chosen person who is screened tests positive.
Given that a person tests positive, find the probability that the person has the condition. Give your answer to 3 significant figures.
State one assumption made in using the figure of 2% for the person being screened, and state the likely effect on your answer to part (b) if the person came from a group in which the condition were more common.
164 exam-style questions on CCEA A Level Maths 4.4 Probability (A-level only), covering 4.4.1 Probability (A-level only), 4.4.2 Probability (A-level only), and 4.4.3 Probability (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.