Solve the problem.A researcher finds a negative correlation between blood pressure and the number of vacations that people take. Can you conclude that taking vacations lowers blood pressure? Propose other explanations for the correlation. Suggest some ways that the researcher could go about establishing causality. Refer to the six guidelines for establishing causality.

Question

What will be an ideal response?

Answer 1

The correlation could be due to a common underlying cause such as income. People with higher incomes tend to take more vacations and also to have access to better health care and to a healthier diet. 

1. Look for a correlation between vacations and blood pressure among various groups - women, men, people of different incomes, ages, races, cultures, lifestyles. 
2. Find two groups which are alike in every respect except the number of vacations they take. Do those who take more vacations have lower blood pressure? Such groups may be difficult to find - people who take more vacations also tend to have access to better health care and to a healthier diet. 
3. Look for evidence that the greater the number of vacations, the lower the blood pressure.
4. Look for evidence that after other potential ways of lowering blood pressure have been accounted for, that the remaining cases occur among those who take many vacations.
5. Conduct an experiment. This may be necessary because of the difficulties mentioned in 2.
6. The researcher should try to determine the physical mechanism by which vacations could lower blood pressure.