Chance Encounters

In this section of the chapter, Paulos tries to use probability to disprove the random element of chance encounters. He uses the example of two strangers meeting on a plane and finding out that one’s wife went to a tennis camp run by the other’s wife’s acquaintance. Paulos used the assumption that if each of the two hundred million adults in the US knew 1,500 people, then there was a 99% chance two people will be connected through a friend of a friend. Initially, Paulos’ argument seems shaky, with too many variables (like the number of acquaintances or the ability to recall them, for example) unaccounted for. However, when he uses the example of birthdays, his proposition seems much more plausible with fewer unexplained elements. If there are 367 people in one room, there is a 100% possibility that one or more of the people share the same birthday. From this, we can conclude that the probability behind a coincidence is determined by how much smaller the number of possibilities are than the number of people in the sample.