Accuracy Versus Precision: The Target Analogy
Accuracy is the degree of veracity while in some contexts precision may mean the degree of reproducibility.
The analogy used here to explain the difference between accuracy and precision is the target comparison. In this analogy, repeated measurements are compared to arrows that are shot at a target. Accuracy describes the closeness of arrows to the bullseye at the target center. Arrows that strike closer to the bullseye are considered more accurate. The closer a system's measurements are to the accepted value, the more accurate the system is considered to be.
To continue the analogy, if a large number of arrows are shot, precision would be the size of the arrow cluster. (When only one arrow is shot, precision is the size of the cluster one would expect if this were repeated many times under the same conditions.) When all arrows are grouped tightly together, the cluster is considered precise since they all struck close to the same spot, even if not necessarily near the bullseye. The measurements are precise, though not necessarily accurate.
However, it is not possible to reliably achieve accuracy in individual measurements without precision—if the arrows are not grouped close to one another, they cannot all be close to the bullseye. (Their average position might be an accurate estimation of the bullseye, but the individual arrows are inaccurate.) See also circular error probable for application of precision to the science of ballistics.
Read more about this topic: Accuracy And Precision
Famous quotes containing the words accuracy, target and/or analogy:
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—Thomas Henry Huxley (1825–95)
“Well gentlemen, this is it. This is what we’ve been waiting for. Tonight your target is Tokyo. And you’re gonna play ‘em the Star Spangled Banner with two-ton bombs. All you’ve got to do is to remember what you’ve learned and follow your squadron leaders. They’ll get you in, and they’ll get you out. Any questions? All right that’s all. Good luck to you. Give ‘em hell.”
—Dudley Nichols (1895–1960)
“The whole of natural theology ... resolves itself into one simple, though somewhat ambiguous proposition, That the cause or causes of order in the universe probably bear some remote analogy to human intelligence.”
—David Hume (1711–1776)