This is an example of the use of buffers to count patients within a specific distance from a given research site. This is a method that could be used to locate cancer victims within specific distances from a chemical release site. In this case, specific high risk locations were identified that were fairly equally spaced from each other, and the distribution of cases relative to each of these spots evaluated descriptively, but not statistically.
The following depicts the different stages of this work in more detail. It is pretty much self-explanatory.