WJEC Maths for AS: Applied sample

2.3 Making predictions using equations of regression lines 31 Examples 1 The scatter diagram below shows data from a random sample of towns in Wales. Number of churches ××× × × × ×× × × × × × × × × ×× Number of deaths from heart attacks (a) Describe the correlation between the number of deaths by heart attack and the number of churches. (b) State whether the relationship shown by the scatter diagram is causal or non-causal. Explain how you decided. Answer 1 (a) Strong positive correlation. (b) Non-causal as number of churches in a town would normally depend on the population of the town and the greater the population of the town, the greater the number of deaths by heart attack. If you decreased the number of churches you would not decrease the number of deaths by heart attack. 2 A researcher found and downloaded a dataset for small sample of illnesses suffered in the UK in 2012. This dataset included the variables: ‘Name of illness’, ‘Annual deaths’ and ‘Name length’, the latter being the number of letters in the name of the illness. (a) The scatter graph represents ‘Annual deaths’ against ‘Name length’. (i) Comment on the correlation between ‘Annual deaths’ and ‘Name length’. [1] (ii) Interpret the correlation between ‘Annual deaths’ and ‘Name length’ in this context. [1] Annual deaths (1000s) 0 5 10 15 20 25 30 35 30 25 20 15 10 5 0 Annual deaths versus name length of illness Name length