EMS certainly lends itself to superstitious thinking (just try saying “it sure is quiet today” around an ambulance station). In this case, it seems the me that the question really isn't what are the odds of getting three out of 11 calls on "gray" street, but instead what are the odds of getting three out of 11 calls on ANY given street, as that would have caught your attention in the same way. I'm too lazy to do the math (the semester just ended after all), but I know from psychological research that people underestimate the probabilities of "unrepresentative" sequences. For example, imagine you put two red, two green and two purple balls in a hat and shake them up. Then, one ball at a time is retrieved at random. Which of the following two sequences is more likely? Sequence A: G,G,P,P,R,R Sequence B: P,G,R,G,P,R Probability theory tells us that the sequences are equally likely, yet most people say Sequence B is more likely than Sequence A, as A does not fit their idea of a "representative" random sample. It is likely that you forget the hundreds of days where you have calls on all different streets, as they fit your idea of a representative call distribution. Likewise, you are likely to note the clustered calls as they violate your representativeness heuristic. Of course a true empiricist would document call sequences over a five year span and then do the analysis. I hope you have better things to do :-). DJ psychonomic.blogspot.com