Studying health risk and perceptions of riskEdexcel A-Level Biology A: Subtopic test

1. 1
   In a study of 5 000 adults aged 50 to 70, researchers recorded whether each person owned a dog and followed all of them for 10 years. The number of deaths from coronary heart disease (CHD) per 1 000 people per year was 2.1 for dog owners and 3.4 for people who did not own a dog.

   (a)

   Which statement is best supported by these data?

   [1 mark]

   • AOwning a dog causes a reduction in the risk of dying from CHD
   • BThere is a positive correlation between dog ownership and death from CHD
   • CThere is a negative correlation between dog ownership and death from CHD
   • DThere is no correlation between dog ownership and death from CHD

   (b)

   Which change would most improve the validity of the comparison between owners and non-owners?

   [1 mark]

   • AMatching the two groups for age, sex, smoking and body mass index
   • BRecruiting only people who already own a dog
   • CReducing the sample to 50 people
   • DIncluding only people who exercise every day

   (c)

   Explain why the researchers cannot conclude that owning a dog reduces the risk of CHD.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   Two towns recorded their deaths from CHD in the same year. Town X has a population of 32 000 and recorded 48 deaths from CHD. Town Y has a population of 12 500 and recorded 30 deaths from CHD.

   (a)

   Calculate the CHD mortality rate for Town X, in deaths per 100 000 people.

   [1 mark]

   • A48
   • B667
   • C1.5
   • D150

   (b)

   Which conclusion is best supported by the data?

   [1 mark]

   • ATown X is at greater risk because it recorded more deaths
   • BTown Y has the higher CHD mortality rate (240 compared with 150 per 100 000), so its residents are at greater risk, even though it recorded fewer deaths
   • CBoth towns are at equal risk because the number of deaths is similar
   • DNo comparison can be made because the populations are different

   (c)

   Calculate how many times greater the CHD mortality rate is in Town Y than in Town X, and suggest one factor, other than the town itself, that could explain the difference.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A researcher wants to find out whether eating a high-salt diet raises blood pressure. She asks for volunteers at a local running club and recruits 20 of them. Ten eat a high-salt diet for four weeks and ten eat their normal diet. She measures each person's blood pressure once, at the end of the four weeks.

   (a)

   Evaluate the way the researcher selected her sample and the size of her sample.

   [3 marks]

   (b)

   Suggest how the design of the investigation could be improved so that the data are more valid and reliable.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   Two studies investigated red meat and CHD. Study 1 followed 120 000 adults for 20 years and used questionnaires to record what they ate. The group with the highest red meat intake had an 18% higher risk of CHD than the group with the lowest intake, after the researchers adjusted for age, smoking and body mass index. Study 2 was a controlled trial in which 400 volunteers ate a diet containing either red meat or white meat for eight weeks. It found no significant difference in LDL cholesterol between the two groups. A separate survey of 1 000 adults found that most rated their own risk of a heart attack as lower than the risk of being the victim of violent crime, and many smokers rated their own CHD risk as lower than that of the average person. In fact, CHD causes far more deaths each year than violent crime, and smoking greatly increases the risk of CHD.

   (a)

   Evaluate how far these two studies provide conflicting evidence about the effect of red meat on the risk of CHD.

   [6 marks]

   (b)

   Explain why people's perceptions of risk from heart disease often differ from the actual risk, referring to the findings of the separate survey.

   [6 marks]

   Total for question 4: 12 marks

End of questions