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The decibel originates from methods used to quantify signal loss in telegraph and telephone circuits. Until the mid-1920s, the unit for loss was miles of standard cable (MSC). 1 MSC corresponded to the loss of power over one mile (approximately 1.6 km) of standard telephone cable at a frequency of 5000 radians per second (795.8 Hz), and matched closely the smallest attenuation detectable to a ...
The SI units are defined by declaring that seven defining constants [1]: 125–129 have certain exact numerical values when expressed in terms of their SI units. The realisation of the definition of a unit is the procedure by which the definition may be used to establish the value and associated uncertainty of a quantity of the same kind as the ...
The data on GI and GL listed in this article is from the University of Sydney (Human Nutrition Unit) GI database. [7] The GI was invented in 1981 by Dr Thomas Wolever and Dr David Jenkins at the University of Toronto and is a measure of how quickly a food containing 25 or 50 g of carbohydrate raises blood-glucose levels.
The minim (abbreviated min, ♏︎ or ♍︎) is a unit of volume in both the imperial and U.S. customary systems of measurement. Specifically, in the imperial system, it is 1 ⁄ 60 of an imperial fluid drachm [1] [2] or 1 ⁄ 480 of an imperial fluid ounce; in the U.S. customary system, it is 1 ⁄ 60 of a US customary fluid dram or 1 ⁄ 480 of a US customary fluid ounce.
In chemistry, concentration is the abundance of a constituent divided by the total volume of a mixture. Several types of mathematical description can be distinguished: mass concentration, molar concentration, number concentration, and volume concentration. [1]
The unit of time should be the second; the unit of length should be either the metre or a decimal multiple of it; and the unit of mass should be the gram or a decimal multiple of it. Metric systems have evolved since the 1790s, as science and technology have evolved, in providing a single universal measuring system.
Level of measurement or scale of measure is a classification that describes the nature of information within the values assigned to variables. [1] Psychologist Stanley Smith Stevens developed the best-known classification with four levels, or scales, of measurement: nominal, ordinal, interval, and ratio.
The g factor [a] is a construct developed in psychometric investigations of cognitive abilities and human intelligence.It is a variable that summarizes positive correlations among different cognitive tasks, reflecting the assertion that an individual's performance on one type of cognitive task tends to be comparable to that person's performance on other kinds of cognitive tasks.