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Measurement is the quantification of attributes of an object or event, which can be used to compare with other objects or events. [1] [2] In other words, measurement is a process of determining how large or small a physical quantity is as compared to a basic reference quantity of the same kind. [3]
In metrology (the science of measurement), a standard (or etalon) is an object, system, or experiment that bears a defined relationship to a unit of measurement of a physical quantity. [1] Standards are the fundamental reference for a system of weights and measures , against which all other measuring devices are compared.
A unit of measurement that applies to money is called a unit of account in economics and unit of measure in accounting. [5] This is normally a currency issued by a country or a fraction thereof; for instance, the US dollar and US cent (1 ⁄ 100 of a dollar), or the euro and euro cent.
Three possible methods of realisation are defined by the international vocabulary of metrology (VIM): a physical realisation of the unit from its definition, a highly-reproducible measurement as a reproduction of the definition (such as the quantum Hall effect for the ohm), and the use of a material object as the measurement standard.
In the SI, the standard metre is now defined as exactly 1 ⁄ 299 792 458 of the distance that light travels in a second. [ 10 ] [ 11 ] The metre can be realised by measuring the length that a light wave travels in a given time, or equivalently by measuring the wavelength of light of a known frequency.
At the close of the 19th century three different systems of units of measure existed for electrical measurements: a CGS-based system for electrostatic units, also known as the Gaussian or ESU system, a CGS-based system for electromechanical units (EMU), and an International system based on units defined by the Metre Convention [33] for ...
Established standard objects and events are used as units, and the process of measurement gives a number relating the item under study and the referenced unit of measurement. Measuring instruments, and formal test methods which define the instrument's use, are the means by which these relations of numbers are obtained.
The standard score in statistics is a signed measure of variance expressed in terms of standard deviations from the mean.; scientists sought to find the most accurate definition for each fundamental measuring units by preparing a model for the measuring unit characterized by the maximum level of accuracy and stability against the time and the environmental changes , these models are called the ...