For an extract of 150 petrol cars, the CO emissions have median 0.24 g/km and interquartile range 0.12 g/km. The extract contains one outlier, a car with a CO emission of 0.72 g/km.
For an extract of 90 diesel cars, the CO emissions have median 0.15 g/km and interquartile range 0.06 g/km, and there are no outliers.
Compare the CO emissions of the petrol cars and the diesel cars in these two extracts.
The car with a CO emission of 0.72 g/km is checked and its value is found to be correct. State, with a reason, whether it should be removed from the extract.
State the effect on the median of the petrol extract of removing that one car.
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.