Email updates

Keep up to date with the latest news and content from IJHG and BioMed Central.

Open Access Research

Relevance of the type III error in epidemiological maps

Harald Heinzl1 and Thomas Waldhoer2*

Author Affiliations

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

For all author emails, please log on.

International Journal of Health Geographics 2012, 11:34  doi:10.1186/1476-072X-11-34

Published: 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.

Directional test decision; Statistical power; Infant mortality; Standardised mortality ratio (SMR); Crude SMR estimator; Unstructured random effect; Structured random effect; BYM model