A student finds strong positive correlation between the CO emission and the CO2 _2\,2 emission of 80 cars. He concludes that a car's CO2 _2\,2 emission causes its CO emission.
State why the student's conclusion is not justified.
Suggest a third factor that could explain why the two emissions are associated.
State what the student would need in order to investigate cause.
157 exam-style questions on AQA A Level Maths 2.2.2 Scatter diagrams and correlation. Each one has a worked solution and a mark scheme showing where the marks go.