Below are the extended notes provided by cognitive psychologist and statistician Barbara Drescher for use in Skepticality Episode 239.  Take a look and leave your comments below. Also, please be sure to listen to the podcast for our own hilarious commentary. Also, visit Barbara’s blog.

I think this is an interesting coincidence! Normally, I would talk about the factors that would increase the probability of this happening, so I will, but there are really very few. People living next door to one another are much, much more alike than two people chosen at random from the global population. They are more likely to be close together in S.E.S. (socioeconomic status), for example. They are more likely to be exposed to similar cultural icons (such as music genres). Factors such as these may exponentially increase the probability of running into each other at just such an event.

However, given the astronomically small base probability (e.g., given all of the people in the world, the probability of any two people, chosen at random, would meet), this is still a story with crazy odds.

Consider the factors that don’t really come into play here, but have in similar stories we have encountered. For example it is unlikely both been inspired to visit by the same event (e.g., hearing a mutual friend talk about visiting Boston). They may have been inspired to visit (assuming the companion was also visiting and not living there) by cheap airfare to the U.S., but then why choose Boston? The probability that they all met each other through mutual friends is greatly reduced by the fact that the Americans know each other because they work together (unless, of course, they knew each other before working there).

So we must rely on the mathematical rule that we should expect at least some low- and even astronomical-probability events to occur in our lives, given the large number of events that occur.