For an extract from the AQA Large Data Set, separate regression lines of CO emission c c\,c g/km on CO2 _2\,2 emission e e\,e g/km are fitted for each fuel type:
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
For both fuel types the CO2 _2\,2 emissions in the extract lie between 100 g/km and 245 g/km.
Find the value of e e\,e for which the two lines predict the same CO emission.
Hence explain why, for every car in the extract, the petrol line predicts a higher CO emission than the diesel line.
Explain why the value of e e\,e found in part (a) has no practical meaning.
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.