A lake is estimated to contain 350 roach, 250 bream, 200 rudd, 150 tench and 450 carp. A biologist proposes taking a stratified random sample of 140 fish, stratified by type.
Give one reason why stratifying by type could improve the sample.
Explain why it may not be possible to carry out stratified random sampling in this context.
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.