SamplingAQA A-Level Maths: Mind map

Exam questions on Sampling

1. A researcher wants to estimate the mean time that students at a sixth-form college of 640 students take to travel to college. One morning she stands at the main entrance and asks the first 30 students who arrive.
   Explain why the mean travel time of her sample may give a misleading estimate of the mean for the whole college.2 marks
2. A teacher has an alphabetical list of the 90 students in Year 12. She numbers them 01 to 90 and uses random numbers to choose a sample of 5 students.
   Her sample of 5 contains 4 boys. The teacher concludes that most Year 12 students are boys. Explain why this conclusion is not justified.2 marks
3. A town has 24 000 registered voters. A polling company wants to estimate the proportion who support a new bypass. Method X: phone 200 voters chosen by applying random numbers to the electoral register. Method Y: ask the first 200 people who walk past a shopping centre on a Saturday morning.
   Compare the two methods, and state which is more likely to give a representative sample of voters.3 marks