A wildlife survey records 180 oystercatchers and 120 redshanks at a coastal site. A stratified random sample of 30 birds is to be health-checked, with species used as the strata.
Calculate the number of oystercatchers that should be selected.
State how many redshanks should be selected.
36 exam-style questions on CCEA A Level Maths 2.4 Statistical sampling, covering 2.4.1 Statistical sampling, 2.4.2 Statistical sampling, 2.4.3 Statistical sampling, and 2.4.4 Statistical sampling. Each one has a worked solution and a mark scheme showing where the marks go.