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Parent Node(s):
VARIABLE
a measurable quantity which at every instant has a
definite numerical value. If there is any doubt whether a
particular quantity may be admitted as a variable, use the
criterion whether it can be represented by a pointer on a dial.
Pressure, angle, electric potential, volume, velocity, mass,
viscosity, population, national income per capita and time
itself, to mention only a few, can all be specified numerically
and recorded on dials. Eddington's statement on the subject is
explicit: "The whole subject matter of exact science consists of
pointer readings and similar indications. Whatever quantity we
say we are 'observing', the actual procedure nearly always ends
in reading the pointer of some kind of indicator on a graduated
scale or its equivalent." (Ashby, 1960, p. l5)
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