Both “accuracy” and “precision” are often used interchangeably in everyday conversation; however, each has a unique meaning. Accuracy defines how correct or how close to the accepted result or standard a measurement or calculation has been. Precision describes how well the results can be reproduced. For example, a person who can repeatedly hit a bull’s eye with a bow and arrow is accurate and precise. If the person’s arrows all fall within a small region away from the bull’s eye, then she or he is precise, but not accurate. If the person’s arrows are scattered all over the target and the ground behind it, the she or he is neither precise nor accurate.