Fig. 4.

Equally detectable potential clusters of various shapes. A most likely cluster of 35 points selected from among the Boston circular cluster data sets, along with its minimum spanning tree, is shown in the upper left. Seven other configurations of 35 points, having minimum spanning trees with exactly the same weight, are also shown. Subject to the constraint imposed by the definition of a potential cluster, all eight clusters have equivalent detectability by the EMST method. If embedded as potential clusters in a Boston data set of 500 total cases, all would achieve the same P value of 0.0001.