An extract from the AQA Large Data Set contains records for 4000 cars. The table below shows how these cars are split by fuel type and by year of registration.
| Earlier year | Later year | Total | |
|---|---|---|---|
| Diesel | 620 | 500 | 1120 |
| Petrol | 1180 | 1700 | 2880 |
| Total | 1800 | 2200 | 4000 |
Rowan selects a sample of 120 of these cars. She chooses the sample so that the number of cars from each of the four groups is in the same proportion as in the extract, rounding each number to the nearest whole number.
Calculate the number of diesel cars from the earlier year in Rowan's sample.
Calculate the number of petrol cars from the later year in Rowan's sample.
Give one advantage of Rowan's method over selecting 120 of the 4000 cars by simple random sampling.
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.