A lake is estimated to contain 350 roach, 250 bream, 200 rudd, 150 tench and 450 carp. A researcher wants a sample of 120 fish to investigate their health.
Explain why stratified random sampling cannot readily be used.
Describe how a sample of 120 could represent the five estimated populations fairly. Name the method.
36 exam-style questions on OCR (MEI) A Level Maths 2.1 Sampling, covering 2.1.1 Population and sample, 2.1.2 Samples to make informal inferences, 2.1.3 Random sampling, 2.1.4 Variety of sampling techniques, 2.1.5 Select or evaluate sampling techniques, and 2.1 Sampling. Each one has a worked solution and a mark scheme showing where the marks go.