A consultant writes the following.
"Analysis of the Large Data Set gives a mean CO emission of 0.14 g/km for diesel cars. Diesel cars in England are therefore cleaner than petrol cars, and this has been the case every year since 2005."
The consultant calculated the mean using only the diesel cars whose CO emission is recorded.
Using your knowledge of the Large Data Set, give two reasons why the claim about diesel cars in England is not supported.
Explain why the claim about every year since 2005 cannot be supported.
Explain how the missing CO emission values could make 0.14 g/km either an underestimate or an overestimate.
State one change to the investigation that would make a conclusion about diesel cars in England defensible.
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.