The measurement error is the deviation of the outcome of a measurement from the true value. For example, if electronic scales are loaded with a 1 kilogram standard weight and the reading is 1002 grams, the measurement error is +2 gram (1002 – 1000).
Measurement error is usually considered as consisting of a systematic error and a random error. According to the type of relationship between measurement error and the true value, errors are subdivided into additive errors and multiplicative errors.
See also the short courses
Introduction to Statistics 1,