For a sample of petrol cars, the CO emissions have mean 0.26 g/km and standard deviation 0.07 g/km.
For a sample of diesel cars, the CO emissions have mean 0.15 g/km and standard deviation 0.04 g/km.
Compare the CO emissions of the petrol cars and the diesel cars.
The largest CO emission in the petrol sample is found to be an error and is removed. State the effect of removing it on the mean and on the standard deviation of the petrol sample.
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.