Relevance of the type III error in epidemiological maps
1 Center for Medical Statistics, Informatics, and Intelligent Systems, Medical University of Vienna, Vienna, Austria
2 Department of Epidemiology, Center for Public Health, Medical University of Vienna, Borschkegasse 8a, A-1090, Vienna, Austria
International Journal of Health Geographics 2012, 11:34 doi:10.1186/1476-072X-11-34Published: 18 August 2012
A type III error arises from a two-sided test, when one side is erroneously favoured although the true effect actually resides on the other side. The relevance of this grave error in decision-making is studied for epidemiological maps.
Theoretical considerations confirm that a type III error may be large for regions with small numbers of expected cases even when no spatial smoothing has been performed. A simulation study based on infant mortality data in Austria reveals that spatial smoothing may additionally increase the risk of type III errors.
The occurrence of a type III error should be taken into account when interpreting results presented in epidemiological maps, particularly with regard to sparsely populated regions and spatial smoothing.