A researcher records the engine capacity and the CO2 _2\,2 emission of 90 cars, all of the same make, and finds a correlation coefficient of 0.78. She concludes that cars with larger engines pollute more.
State two things the value 0.78 does not tell the researcher.
Explain how the fact that all 90 cars are of the same make limits her conclusion.
Describe a study that would allow higher CO2 _2\,2 emissions to be attributed to engine capacity itself.
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.