Scientists investigated coronary heart disease in 600 adult members of one leisure centre. During a 10-year study, 18 of the adults developed coronary heart disease.
The table compares the exercise habits of the sample with those of all adults in the country.
| Group | Adults who exercise on at least three days each week (%) |
|---|---|
| Leisure-centre sample | 78 |
| All adults in the country | 31 |
Calculate the incidence of coronary heart disease in the leisure-centre sample as a percentage.
Explain why the calculated value may not be valid for all adults in the country. Predict whether the true national incidence is likely to be higher or lower than the calculated value.
304 exam-style questions on AQA GCSE Biology 2.2 Animal tissues, organs and organ systems, covering 2.2.1 The human digestive system, 2.2.2 The heart and blood vessels, 2.2.3 Blood, 2.2.4 Coronary heart disease: a non-communicable disease, 2.2.5 Health issues, 2.2.6 The effect of lifestyle on some non-communicable diseases, and 2.2.7 Cancer. Each one has a worked solution and a mark scheme showing where the marks go.