b) i) There are two dependent variables. (1 mark) ii) So that the relationship between the number of cigarettes smoked and the number of deaths from lung cancer can be displayed. (1 mark)
c) As the number of cigarettes smoked increased, so the number of deaths from lung cancer also increased, but many years later. (1 mark) As the number of cigarettes smoked decreased, so the number of deaths from lung cancer also decreased, but many years later. (1 mark)
d) Because cigarette smoking has a cumulative effect, it takes a number of years of smoking for harmful chemicals (carcinogens) in tobacco to build up to a level where they cause cancer. (1 mark) Lung cancer is a progressive disease and it is often many years before its symptoms are noticed and many more years before it causes death. (1 mark)
e) Tobacco smoke reduces the oxygen-carrying capacity of the blood (by combining more readily with haemoglobin than oxygen does). (1 mark) The information in brackets is not essential to obtain the mark but is the sort of detail that a higher-level candidate might be expected to provide.
6 a) 8.8 + 5.2 + 3.8 + 3.3 = 21.1% (1 mark) The question says ‘more than’ and so candidates are expected to add the four larger categories of units drunk (7–10, 11–14, 15–20 and 21+) for 14 year olds. Common errors are adding in the 1–6 category as well or using the wrong age group. Students are not asked to show their working and so just the answer ‘21.1%’ will suffice.
