Scientists wanted to find out whether there is a link between long-term stress at work and the incidence of coronary heart disease. They studied 60 people who all worked in the same office. All 60 people were men aged 45 to 55.
Give two reasons why this study may not give a valid conclusion about the whole population.
The scientists also recorded the diet and the amount of exercise of each person in the study.
Explain why they needed this information.
The scientists found a positive correlation between the level of stress and the incidence of coronary heart disease.
Explain why this does not show that stress causes coronary heart disease.
179 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.