According to the U.S. Census, roughly half of all marriages in the United States end in divorce. Researchers from leading universities have shown that the emotions aroused by one person’s divorce can transfer like a virus, making divorce contagious (CNN, June 10, 2010). A split-up between immediate friends increases a person’s own chances of getting divorced from 36% to 63%, an increase of 75%. Use these findings to answer the following questions.

a. Compute the probability that more than half of four randomly selected marriages will end in divorce.

b. Redo part a if it is known that the couple’s immediate friends have split up.

c. Redo part a if it is known that none of the couple’s immediate friends has split up.