Difficulty guide
The label describes the problem, not your ability.
1/5 - Foundational
Warm-up setup; checks one basic idea.
2/5 - Routine exam skill
Normal syllabus skill; usually one main rule or interpretation.
3/5 - Standard multi-step
Exam-style problem with multiple steps or a common trap.
4/5 - Hard exam skill
High-end exam problem; combines methods carefully.
5/5 - Challenge
Stretch problem beyond normal exam pressure.
Question
(a) Find the probability that a randomly selected person tests positive. (2 marks)
(b) Given a positive result, find the probability that the person has the disease. (1 mark)
(c) Given a positive result, find the probability that the person does not have the disease. (1 mark)
(d) Given a negative result, find the probability that the person has the disease. (1 mark)