SUGGESTED ANSWER TO QUESTION 2A-3(a)

Although it is possible that stress is causing the bodies of these men to deteriorate over time, it also is possible that the passage of time itself and the natural aging of the body is the real culprit. The passage of four to eight years during middle age can lead to dramatic changes in the appearance of a person, regardless of whether or not the person is experiencing severe stress.

In order to see if the stress of the president's job is causing the changes, we would need to compare the pictures of presidents over 4-8 years with the pictures of people of the same age over the same number of years. We also would need to control for the expectations of the observers who are making the judgements because, if they have the expectation that severe stress will lead to more rapid aging of the body, they may judge the presidents to be aging more rapidly than the others.