feilstørrelsen

Feilstørrelsen is a term used in metrology and measurement practice to describe the magnitude of deviation between a measured value and the true value. Because the true value is often unknown, feilstørrelsen is typically expressed in terms of absolute error or relative error, for example ε = |M − T| or ε_rel = |M − T|/|T|, where M is the measured value and T is the true value.

In measurement theory, feilstørrelsen comprises different components. Systematic error (bias) leads to a consistent offset from the true value, while random error causes scattered results around the true value. The overall feilstørrelsen can be characterized by statistics derived from repeated measurements, such as the mean error (to assess bias) and the standard deviation (to describe random variation). When many measurements are available, the standard error and confidence intervals are used to express the uncertainty associated with the measured value.

Estimation and calibration are central to managing feilstørrelsen. Repeated measurements, instrument calibration, and environmental control help separate bias from random error and reduce the overall size of the error. In practice, feilstørrelsen informs quality control, comparative testing, and uncertainty propagation in calculations that rely on measurement data. It is closely related to the broader concept of measurement uncertainty, which aims to quantify all sources of doubt in a reported result.

Feilstørrelsen is often discussed alongside accuracy (closeness to the true value) and precision (repeatability of measurements). Together, these concepts guide the assessment and improvement of measurement instruments and procedures.