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Visualization Technique for Uncertainty Budgets: Onion Charts



Kenneth W. Pratt, David L. Duewer


A concise graphical depiction, the onion chart, is described for presenting uncertainty budgets for any measurand, y, having a set of component variances, ui2(y). The onion chart consists of a concentric series of rings. Each ring is constructed from the set of fractional contributions, ui2(y)/?ui2(y). The outer ring includes all ui2(y) and depicts the combined standard uncertainty, uc(y), where uc2(y) = ?ui2(y). Moving inward, each successive ring deletes the largest remaining ui2(y). A reduced ?ui2(y) is calculated for that ring from the remaining set of ui2(y), with the fractional contributions calculated using the reduced ?ui2(y). This format facilitates rapid visual comparison of the contributions from each component, with minor components becoming visible as the larger components are successively deleted. An example is presented using data from pH metrology, including the physical interpretation of the resulting diagram.
Analytical Chemistry


doughnut chart, graphical tool, ISO GUM, onion chart, pH metrology, pie chart, uncertainty analysis


Pratt, K. and Duewer, D. (2008), Visualization Technique for Uncertainty Budgets: Onion Charts, Analytical Chemistry (Accessed March 2, 2024)
Created October 16, 2008