The most unusual coincidence in my life took place when I flew from Boston, my home, to Chicago to meet Scott Isenberg, the new editor assigned to revise a statistics textbook I had authored a few years earlier. We were having dinner at a restaurant overlooking Lake Michigan, and Scott began to talk nostalgically about the orange groves that graced his neighborhood in a small town in California, where he grew up. I recalled that my wife, Debra, who is also from California, used to talk about orange groves as well. We both smiled and continued our conversation—after all, the state has 38 million people. But every remark he made about his childhood abode reminded me of something that my wife had told me. As we continued to notice more of these coincidences, I told him Debra’s name and he literally jumped out of his chair. It turned out that they had been friends in high school. You might think, what is the probability of such a rare event? It may be one in many millions.
The simple question might be “why do such unlikely coincidences occur in our lives?” But the real question is how to define the unlikely. You know that a situation is uncommon just from experience. But even the concept of “uncommon” assumes that like events in the category are common. How do we identify the other events to which we can compare this coincidence? If you can identify other events as likely, then you can calculate the mathematical probability of this particular event as exceptional.
More here – Nautilus