The CO2 _2\,2 emissions, x x\,x g/km, of the cars in two extracts are summarised below.
Extract A contains 40 cars, with ∑x=8400\sum x = 8400∑x=8400 and ∑x2=1 780 000\sum x^2 = 1\,780\,000∑x2=1780000.
Extract B contains 60 cars, with ∑x=10 800\sum x = 10\,800∑x=10800 and ∑x2=1 968 000\sum x^2 = 1\,968\,000∑x2=1968000.
Find the mean and the standard deviation of the CO2 _2\,2 emissions in extract A.
Find the mean and the standard deviation of the CO2 _2\,2 emissions in extract B.
Find the mean and the standard deviation of the CO2 _2\,2 emissions of all 100 cars.
Explain why the standard deviation found in part (c) is greater than the standard deviation of either extract on its own.
105 exam-style questions on WJEC A Level Maths 2.2 Data presentation and interpretation, covering 2.2.1 Data presentation and interpretation, 2.2.2 Data presentation and interpretation, 2.2.3 Data presentation and interpretation, 2.2.4 Data presentation and interpretation, 2.2.5 Data presentation and interpretation, 2.2.6 Data presentation and interpretation, 2.2.7 Data presentation and interpretation, 2.2.8 Data presentation and interpretation, and 2.2 Data presentation and interpretation. Each one has a worked solution and a mark scheme showing where the marks go.