Measurement

Measurement assigns values to quantities by comparing them with defined units or applying specified methods. Its results depend on the quantity’s definition, the measurement procedure, and the limits of instruments.

Physical quantity: A property of a system that can be expressed as a number and a unit. Measurement assigns values to quantities defined as measurable properties.
Measurand: The quantity intended to be measured in a particular measurement procedure. A procedure must specify which quantity its result is meant to represent.
Measurement uncertainty: A parameter describing the dispersion of values reasonably attributable to a measured quantity. It expresses the limits of knowledge surrounding a reported measurement result.
Metrology: The science of measurement, including its theory, methods, and practical realization. Metrology develops the standards and methods that make measurements comparable.
Qualitative research: Research that analyzes nonnumerical data to understand meanings, experiences, or social processes. It can investigate phenomena that numerical measurement alone does not capture.
Unit of measurement: A defined reference amount used to express the magnitude of a quantity. A result states how many units correspond to the measured quantity.
Measurement procedure: A detailed set of operations used to obtain a measurement result. The procedure fixes how the target quantity is observed and calculated.
Measurement error: The difference between a measured value and a reference value for the same quantity. Errors explain why a result can differ from the quantity’s reference value.
Scientific method: A systematic approach to investigating questions through observation, hypothesis, and testing. Quantitative measurements provide evidence for evaluating scientific explanations.
Estimation: The process of inferring an approximate value from incomplete or uncertain information. Estimation often supplies values when direct measurement is unavailable or impractical.

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