22 Apr

Accuracy and Precision

Many laboratory items are defined by their accuracy and their precision.  These items include but are not limited to pipettes,  volumetric glassware, balances, spectrophotometers. . .  Accuracy expresses how close the measurement is to the true value.  Precision expresses how close the repeated measurements of a single sample are to each other.  The bull’s eye example is the classic explanation of precision VS. accuracy.  If an archer is hitting points all over the bull’s eye he is neither accurate nor precise.  If his hits are centered around the bull’s eye but are scattered he is accurate but not precise.  If all his hits are very close to each other but not near the bull’s eye he is precise but not accurate(something is wrong with the bow, a systemic error).  If he has all of his points within the bull’s eye and very close to each other he is both precise and accurate.

Robin Prymula