NOTES
What I've done here is simulate the occurrence of some kind of phenomenon - let's say occurrence of a particular disease. The stars represent areas where the occurrence of the disease is about twice the average frequency - there's got to be a cause for that, right? And the square represent some suspicious item - a power plant, a trash incinerator, or something of that ilk. Someone living here, or here is going to suspect a connection between the incinerator and the cluster of disease occurrences, but in this case, I know there's no connection - I laid down the disease occurrences and the incinerator locations completely randomly. But given that there are hundreds of possible diseases, and hundreds of potential suspicious items, sheer chance will find plenty of cases where the correlation between car dealerships, or libraries or science fiction convention sites and some disease is quite high.