Definition of Accuracy:

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  1. Accuracy refers to clustering of data about a known target. It is the difference between a physical quantity’s average measurements and that of a known standard, accepted ‘truth’ vs. ‘benchmark.’ Envision a target with many arrows circling the bullseye, however, none of them are near each other.
  2. Precision refers to the tightness of the cluster of data. Envision a target with a cluster of arrows all touching one another but located slightly up and to the right of the bullseye.

In practice it is easier to correct a process which has good precision than it is to correct a process which is accurate. This is due to the increased amount of variation associated with accurate but not precise process.

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