Plusmiinusarvon

Plusmiinusarvon, in English often referred to as the plus–minus value, is a notation used to express the uncertainty of a reported measurement by pairing a central value with a margin of error. It conveys that the true value is expected to lie within a symmetric (or sometimes asymmetric) interval around the reported value. A typical form is value ± uncertainty, for example 12.50 cm ± 0.03 cm.

Notation and variants: The standard form is a central value followed by the plus–minus symbol and the uncertainty. If uncertainties are not symmetric, the notation may appear as value +a/−b, indicating different positive and negative limits. The plus–minus convention is common across scientific disciplines, including physics, chemistry, engineering, and metrology, where it communicates precision and reliability of measurements.

Purpose and interpretation: The plus–minus value communicates both the measured value and the range within which the true value is expected to lie, often at a stated confidence level. It helps compare results, assess measurement quality, and propagate uncertainty through calculations. The reported uncertainty typically reflects random (statistical) errors, systematic errors, or a combination, depending on the method used to estimate it.

Determination and limitations: Uncertainties can be estimated from repeated measurements (giving standard deviation), instrument specifications, calibration data, or formal uncertainty propagation. Limitations include the assumption of symmetry, potential neglect of correlations, and the fact that the interval does not guarantee the true value with exact probability unless a formal confidence interval has been specified.

See also: measurement uncertainty, error analysis, standard deviation, confidence interval, propagation of uncertainty.