An extract from a vehicle database contains 1440 cars of three makes, A, B and C, in the ratio 3:4:53 : 4 : 53:4:5.
Nadia takes a sample of 96 of these cars, with each make represented in proportion to its size in the extract.
Calculate the number of cars of each make in Nadia's sample.
The mean CO emissions of the sampled cars of makes A, B and C are 0.18 g/km, 0.24 g/km and 0.33 g/km respectively. Calculate the mean CO emission of all 96 cars in Nadia's sample.
State one assumption needed for the answer to part (b) to be a reliable estimate of the mean CO emission of all 1440 cars in the extract.
28 exam-style questions on AQA A Level Maths 2.1 K: Statistical sampling, covering 2.1.1 Populations, samples and sampling techniques. Each one has a worked solution and a mark scheme showing where the marks go.