Scientists carried out an observational study of adults exposed to different levels of air pollution. The adults were followed for eight years.
| Exposure to air pollution | Number of adults | Number developing lung disease |
|---|---|---|
| High | 600 | 54 |
| Low | 900 | 45 |
Calculate the relative risk of developing lung disease for adults with high exposure compared with adults with low exposure.
Explain why these results are not enough to show that high exposure to air pollution caused the difference in lung disease.
102 exam-style questions on Edexcel GCSE Biology 5.4 Non-communicable diseases, covering 5.4.1 Interaction of factors in non-communicable disease, 5.4.2 Lifestyle factors and non-communicable disease, and 5.4.3 Treatments for cardiovascular disease. Each one has a worked solution and a mark scheme showing where the marks go.