A lake contains five different types of fish.
There are an estimated 350 Roach, 250 Bream, 200 Rudd, 150 Tench and 450 Carp.
John wishes to investigate the health of the fish in the lake.
He decides to take a sample of 120 fish.
Give a reason why stratified random sampling cannot be used.
Explain how a sample of size 120 could be taken to ensure that the estimated populations of each type of fish are fairly represented.
You should state the name of the sampling method used.
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.