A clerk brags to the boss, "I am precise in parking my car; it is always in the exact center ofthe space." The boss responds, "Yes, but you are not accurate; you often park in my space.
Some familiar and useful words may lead to discussion such as this when the words have a variety of meanings. Precise ordinarily means meticulous or fastidious; to a machinist it implies a closely fitted machine part. In a laboratory, precision may denote the exactness of a measurement (eg, glucose within 0.1 mmol/L), or it may relate to the number of significant digits used (eg, 5.1 mmol/L or 5.12 mmol/L). In some contexts precision implies the closeness (consistency) of repeated measurements of the same substance or object. If systematic error (bias) is present, repeated measurements may be closely clustered, but displaced from the truth, ie, they are precise but