A study records whether adults have obesity and a viral infection at the start. The researchers do not alter either factor. The groups are followed for 10 years.
| Obesity | Viral infection | Number of adults | Number who develop liver disease |
|---|---|---|---|
| no | no | 1200 | 12 |
| yes | no | 1000 | 30 |
| no | yes | 800 | 32 |
| yes | yes | 600 | 72 |
Calculate the difference, in percentage points, between the percentage who develop liver disease in the group with both factors and the percentage in the group with neither factor.
Explain why the results support the conclusion that obesity and viral infection can interact to increase the risk of liver disease, but do not show that either factor caused the 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.