Measures and accuracy Study Guide

A rounded or measured value represents a range of possible actual values. If a value is rounded to the nearest unit, subtract half a unit for the lower bound and add half a unit for the upper bound. The lower bound is included, while the upper bound is normally excluded because values at or above it would round to the next value. For a value rounded to the nearest 0.1, the half-unit is 0.05.

Rounding replaces a value with a nearby stated value, while truncation cuts off digits without increasing the retained part. For a positive value rounded to a stated unit, the true value lies from half a unit below the displayed value, inclusive, to half a unit above it, exclusive. For positive truncation to a unit, the true value is at least the displayed value but less than one unit above it.