Relevance of the type III error in epidemiological maps.
BACKGROUND
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.


RESULTS
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.


CONCLUSIONS
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.
Center for Medical Statistics, Informatics, and Intelligent Systems, Medical University of Vienna, Vienna, Austria.
Harald
H
Heinzl
Thomas
T
Waldhoer
D001317:Austria / Q000453:epidemiology; D015982:Bias; D003627:Data Interpretation, Statistical; D062305:Geographic Mapping; D006801:Humans; D007223:Infant; D007226:Infant Mortality; D015233:Models, Statistical