A developmental psychologist wants to investigate peer-group influence on risk-taking behaviour in adolescents. The target population consists of 1,200 1,200\,1,200 pupils at a secondary school: 400 in Year 10, 500 in Year 11, and 300 in Year 12. The psychologist decides to obtain a sample of 120 pupils using stratified sampling based on Year group.
Which option correctly states the number of Year 11 pupils required for this sample and describes how a truly random sample would be obtained from within this stratum?
505050 pupils; assign each Year 11 pupil a unique number from 111 to 500500500 and use a computerised random number generator to select 505050 numbers.
505050 pupils; select every 10th10^{\text{th}}10th pupil from an alphabetical roster of all Year 11 pupils.
404040 pupils; assign each Year 10 pupil a unique number from 111 to 400400400 and use a computerised random number generator to select 404040 numbers.
505050 pupils; display a poster in the Year 11 common room and select the first 505050 pupils who volunteer to participate.
644 exam-style questions on OCR A Level Psychology Research methods and techniques. Each one has a worked solution and a mark scheme showing where the marks go.