Bea uses the AQA Large Data Set to estimate the mean CO emission of diesel cars. In the region she chooses there are 340 diesel cars, but the CO emission is recorded for only 296 of them.
State the value Bea should divide the sum of the recorded CO emissions by, and give a reason.
Explain the effect on Bea's estimate of instead treating each missing value as 0 g/km.
Using your knowledge of the Large Data Set, give one reason why Bea's estimate should not be quoted as the mean CO emission of diesel cars in England.
28 exam-style questions on AQA A Level Maths 2.1 K: Statistical sampling, covering 2.1.1 Populations, samples and sampling techniques. Each one has a worked solution and a mark scheme showing where the marks go.