Right now, this question is marked for closing as a duplicate of this one. Yet the titles and subjects are totally different at first glance - and someone searching for something similar will have little hope of finding this.
Of course, a little thought makes us realize both are about analyzing coincidences. But we don't have such a tag (at least, I could not find one) and neither of the two questions is really canonical.
Should we have some question such as "How can one analyze the probability of coincidences?" ? Or should we just add a tag?