Accuracy is a measure of how close a given set of measurements are to their true value. It refers to the degree of closeness between a measurement and its true value. In other words, accuracy is the freedom from mistake or error. It is obtained by taking small readings, which reduces the error of the calculation. Accuracy is often used in industrial instrumentation to describe the measurement tolerance or transmission of the instrument, and it defines the limits of the errors made when the instrument is used in normal operating conditions.
Precision, on the other hand, is a measure of how close the measurements are to each other. It refers to the degree to which repeated measurements under the same conditions show the same results. Precision is often used in military terms to refer to the precision of fire expressed by the closeness of a grouping of shots at and around the center of the target. A good analogy for understanding accuracy and precision is to imagine a football player shooting at the goal. If the player shoots into the goal, he is said to be accurate. A football player who keeps striking the same goalpost is precise but not accurate. Therefore, a football player can be accurate without being precise if he hits the ball all over the place but still scores. A precise player will hit the ball to the same spot repeatedly, irrespective of whether he scores or not.
In summary, accuracy is a measure of how close a given set of measurements are to their true value, while precision is a measure of how close the measurements are to each other.
