Do well-rounded people get fewer colds? A study on the Chronicle of Higher Education was conducted by scientists at Carnegie Mellon University, the University of Pittsburgh, and the University of Virginia. They found that people who have only a few social outlets get more colds than those who are involved in a variety of social activities. Suppose that of the 276 healthy men and women tested, n1 = 96 had only a few social outlets and n2 = 105 were busy with six or more activities. When these people were exposed to a cold virus, the following results were observed:

a. Construct a 99% confidence interval for the difference in the two population proportions.
b. Does there appear to be a difference in the population proportions for the two groups?
c. You might think that coming into contact with more people would lead to more colds, but the data show the opposite effect. How can you explain this unexpected finding?

Few Social Outlets 96 62% Many Social Outlets 105 35% Sample Size Percent with Colds