A factory has 720 workers on a list formed by repeating the same sequence of 12 job roles. A manager chooses a random starting position from 1 to 12 and then selects every 12th worker until 60 workers have been chosen.
State the sampling technique and explain why 12 is the intended interval.
Explain why the ordering of this list could make the sample seriously biased.
Suggest one modification that would reduce this problem.
36 exam-style questions on OCR A Level Maths 2.1 Statistical Sampling, covering 2.1.1 Population and sample, 2.1.2 Informal inferences from samples, 2.1.3 Sampling techniques, 2.1.4 Selecting or critiquing sampling techniques, and 2.1 Statistical Sampling. Each one has a worked solution and a mark scheme showing where the marks go.