Priya is using the Large Data Set.
She wants to test whether the proportion of diesel cars with CO emissions greater than 0.5 g/km is different for two different makes of car, and then to apply her conclusion to all cars in the United Kingdom.
Using your knowledge of the Large Data Set, give two reasons why Priya cannot carry out this test using the Large Data Set.
Priya decides instead to compare the mean CO emissions of petrol cars in the two registration years covered by the Large Data Set. She finds the mean is lower in the later year and concludes that cars are becoming cleaner. Give two reasons why her data do not justify this conclusion.
Priya finds that the CO emission value is missing for a number of the diesel cars. She decides to delete every car whose CO emission value is missing. Explain one risk in doing this.
State one modelling assumption Priya must make if she treats the Large Data Set as a random sample of cars registered in England.
244 exam-style questions on AQA A Level Maths 2.2 L: Data presentation and interpretation, covering 2.2.1 Single-variable data diagrams, 2.2.2 Scatter diagrams and correlation, 2.2.3 Central tendency, variation and standard deviation, 2.2.4 Outliers and cleaning data, and 2.2 L: Data presentation and interpretation. Each one has a worked solution and a mark scheme showing where the marks go.