There are two types of measures.

Discrete measures can be counted (such as people, or cars).

Continuous measures involve measurement (such as the length of a car, or the weight of a person) where a single measure can fall into a range.

The accuracy of a continuous measurement depends upon the person or device making the measurement. Sometimes this is stated as 25m to the nearest 1m. This can be written as 24.5 ≤ l < 25.5. Half of the nearest 1m goes above the given value, and half goes below.

In engineering, a measurement is often given with an error interval or tolerance: for example, a length may be given as 25cm ±0.5mm: this describes the accuracy of the measurement in a slightly different way.

However it is stated, the range is the Limit of Accuracy for that measurement.

The Limit of Accuracy gives us two additional values. If m is the measurement and t is the tolerance, then:

lower bound = m - 0.5t; and

upper bound = m + 0.5t.