Solve the problem.A researcher finds a positive correlation between the amount of coffee people drink and anxiety level. Can you conclude that drinking coffee causes anxiety? 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 the level of stress in a person's life. Those with stressful, demanding jobs for example are likely to have more anxiety and are also likely to drink more coffee. 

The following are ways of establishing causality. 
1. Look for a correlation between coffee drinking and anxiety among various groups - women, men, people of different incomes, ages, races, cultures, lifestyles, professions. 
2. Find two groups which are alike in every respect except the amount of coffee they drink. Do those who drink more coffee have higher levels of anxiety? Such groups may be difficult to find.
3. Look for evidence that the more coffee people drink, the higher their anxiety level.
4. Look for evidence that after other potential causes of anxiety have been accounted for, that the remaining cases occur among those who drink a lot of coffee.
5. Conduct an experiment. This may be necessary because of the difficulties mentioned in 2. But consideration should also be given to whether an experiment would be ethical.
6. The researcher should try to determine the physical mechanism by which coffee causes anxiety.