## VARIETY
^{1)}^{2)}

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1)"Given a set of elements… the number of elements that can be distinguished" (W.R. ASHBY, 1951, p.167).

2)"A measure of uncertainty or the amount of selection needed to remove the uncertainty" (G. PASK, 1960, p.116).

ASHBY explains: "Thus the set {gbcggc} has a variety of 3 letters… For many purposes the variety may be more conveniently measured by the logarithm of this number. If the logarithm is taken to base 2, the unit is the bit. The context will make clear whether the number or its logarithm is being used as measure" (Ibid).

Generally it is now understood that the measure of variety is expressed in bits. Using this base, a bit is the quantity of information needed to reduce uncertainty by half. (thus the connection between ASHBY's and PASK's definitions).

Variety as a concept may look deceptively trivial. However, a still quite simple system, as ASHBY's homeostat, with 4 elements and 25 different possible positions for each of them offers already a variety of 25, i.e. 390.625 combinations. Really complex system's variety overcomes our imagination and, in order to give them some definition, constraints become an absolute necessity.

### Categories

- 1) General information
- 2) Methodology or model
- 3) Epistemology, ontology and semantics
- 4) Human sciences
- 5) Discipline oriented

### Publisher

Bertalanffy Center for the Study of Systems Science(2020).

To cite this page, please use the following information:

* Bertalanffy Center for the Study of Systems Science (2020).* Title of the entry. In Charles François (Ed.), International Encyclopedia of Systems and Cybernetics (2). Retrieved from www.systemspedia.org/[full/url]

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