title: The geography of power: statistical performance of tests of clusters and clustering in heterogeneous populations.
abstract: Heterogeneous population densities complicate comparisons of statistical power between hypothesis tests evaluating spatial clusters or clustering of disease. Specifically, the location of a cluster within a heterogeneously distributed population at risk impacts power properties, complicating comparisons of tests, and allowing one to map spatial variations in statistical power for different tests. Such maps provide insight into the overall power of a particular test, and also indicate areas within the study area where tests are more or less likely to detect the same local increase in relative risk. While such maps are largely driven by local sample size, we also find differences due to features of the statistics themselves. We illustrate these concepts using two tests: Tango's index of clustering and the spatial scan statistic. Furthermore, assessments of the accuracy of the 'most likely cluster' involve not only statistical power, but also spatial accuracy in identifying the location of a true underlying cluster. We illustrate these concepts via induction of artificial clusters within the observed incidence of severe cardiac birth defects in Santa Clara County, CA in 1981.
authors.affiliation: Department of Biostatistics, Rollins School of Public Health, Emory University, 1518 Clifton Road NE, Atlanta, GA 30322, USA. lwaller@sph.emory.edu
authors.forename: Lance A
authors.initials: LA
authors.lastname: Waller
authors.forename: Elizabeth G
authors.initials: EG
authors.lastname: Hill
authors.forename: Rose Anne
authors.initials: RA
authors.lastname: Rudd
mesh_terms: D002140:California / Q000453:epidemiology; D018376:Cardiovascular Abnormalities / Q000453:epidemiology; D016000:Cluster Analysis; D003198:Computer Simulation; D000013:Congenital Abnormalities / Q000453:epidemiology; D003627:Data Interpretation, Statistical; D004196:Disease Outbreaks; D006801:Humans; D007231:Infant, Newborn; D011157:Population Dynamics; D014874:Water Pollutants, Chemical / Q000009:adverse effects
chemical_list: D014874:Water Pollutants, Chemical