Age-adjusted diabetes prevalence among adult African American Medicaid recipients (base map) with associated 95 percent confidence intervals (rings). The base map in the center of the figure shows age-adjusted diabetes prevalence rates for adult African American Medicaid recipients at the county level. Prevalence rate classes represent quartiles of the county-level prevalence rate distribution. Prevalence rate quartiles are symbolized using an orange color ramp in the base map, and for graphic differentiation a gray color ramp in the rings surrounding the base map. Superimposed on the rings, a set of 95 percent confidence interval symbols, each consisting of a central square and two extending "arms," shows the age-adjusted diabetes prevalence rate (square) and the 95 percent confidence interval associated with that rate for each county. The ring map differentiates counties with relatively wide versus narrow 95 percent confidence intervals (e.g., Oconee versus Anderson in the northwest portion of the state), highlights instances in which the 95 percent confidence interval extends through multiple quartile ranges (e.g., Cherokee in the northern part of the state), and shows where the 95 percent confidence intervals of counties grouped in different quartiles overlap (e.g., Abbeville and Greenwood in the western part of the state).
Stewart et al. International Journal of Health Geographics 2011 10:18 doi:10.1186/1476-072X-10-18