Cluster: a software system for epidemiologic cluster analysis.

A software package for cluster analysis was developed that incorporates 12 methods to analyse residence and time data, and morbidity or mortality rates. The Knox, Barton, Chen and Ohno methods of the software are illustrated with data for 123 cancer cases reported by a citizen requesting a cluster investigation. Longitude and latitude for each address were assigned by a geographic information system for analyses with the Barton (p > 0.05) and Knox methods (p > 0.05). The data were also analysed for time of the event with the Chen method, comparing the observed incidence to expected county disease rates (p = 0.61), and for temporal patterns within the geographically defined population with the Ohno method (p >0.05). It was concluded that no statistically significant disease cluster existed.