For the cars in an extract from the AQA Large Data Set, separate regression lines are fitted for each fuel type. With c c\,c the CO emission in g/km and e e\,e the CO2 _2\,2 emission in g/km, the two lines are
diesel cars: c=0.02+0.0009ec = 0.02 + 0.0009ec=0.02+0.0009e
petrol cars: c=−0.18+0.0032ec = -0.18 + 0.0032ec=−0.18+0.0032e
Interpret the two gradients in context, and state which fuel type shows the greater increase in CO emission for a given increase in CO2 _2\,2 emission.
Explain why comparing the two numbers 0.02 and -0.18 is not useful here.
Use the appropriate line to estimate the CO emission of a diesel car whose CO2 _2\,2 emission is 130 g/km, and state whether your answer is consistent with the Large Data Set.
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.