Besag and Newell's method can detect local or global spatial clusters in group-level data. When you initiate a Besag and Newell analysis in ClusterSeer, you get both local and global analysis output. While individual- or case-level analysis is theoretically possible with this method, ClusterSeer implements only the region-centered group-level technique.
This method scans the data for collections of cases that appear to be unusual clusters. To do so, it centers a circular window on each region in turn. This window is then expanded to include neighboring regions until the total number of cases in the window reaches a user-specified threshold, k. Then, the population size inside the window is compared to that expected under an average or expected disease frequency.
Example Applications
Besag and Newell (1991) use the method to screen for clusters of childhood leukemia in northern England, and they found no evidence for clustering of leukemia cases in the years surveyed (1975-85). Waller et al. (1994) use it to survey patterns in leukemia in upstate New York. They did not find strong evidence for clustering, though there was a suggestion of some clustering in one county. They recommend using the method to prioritize areas for further study. Le, Petkau, and Rosychuk (1996) use a modification of the method to examine whether cancer clusters appear near pulp and paper mills in British Columbia, Canada. The method successfully re-identified several known clusters of different types of cancers.
