Exercises

•    The investigator undertakes a case control study to address the research question, Does eating more fruits and vegetables reduce the risk of coronary heart disease (CHD) in the elderly? Suppose that her study shows that people in the control group report a higher intake of fruits and vegetables than people with CHD.
•    What are the possible explanations for this inverse association between intake of fruits and vegetables and CHD? How could each of these possibilities be altered in the design phase of the study? How could they be addressed in the analysis phase?
•    Give special attention to the possibility that the association between eating fruits and vegetables and CHD may be confounded by exercise (if people who eat more fruits and vegetables also exercise more and this is the cause of their lower CHD rates). What approaches could you use to cope with exercise as a possible confounder, and what are the advantages and disadvantages of each plan?