Question 5
The scatter diagram below shows the CO2 _2\,2 emission and the CO emission, both in g/km, of 58 cars from an extract of the AQA Large Data Set.
For all 58 cars, the correlation coefficient between CO2 _2\,2 emission and CO emission is 0.86.
For the 28 cars in the lower left group the correlation coefficient is -0.94, and for the 30 cars in the upper right group it is -0.85.
a.[2]
State which variable in the Large Data Set the two groups correspond to, and identify which group contains the diesel cars, with a reason.
b.[1]
Describe the correlation within each of the two groups.
c.[3]
Explain how the correlation coefficient for all 58 cars can be strongly positive when it is strongly negative within each group.
d.[1]
State what should be done before any single correlation coefficient is quoted for these data.
2.2 L: Data presentation and interpretation Questions
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.