Answer to Question #29184 in Statistics and Probability for Paul Adams

Question

This isn't for an assignment but to settle a discussion and satisfy curiosity. In light of the terrible events in Boston some friends have claimed that the odds of 8 terror attacks around the globe coinciding with anti-terror drills in the same city are beyond astronomical. Once claim - entirely unsupported by any figures - was that it was a figure greater than all the molecules int he known universe to one against such a multiple coincidence. Intuitively this seems vaguely plausible although clearly off by many orders of magnitude. However my experience has taught me not to trust intuition when probability is concerned. I am sure they are falling prey to some kind of logical fallacy or cognitive bias.

So, can you shed some light on this subject? What are the odds on 8 terrorist attacks around the globe occurring on the same day and in the same city as anti-terror drills?