Ordinal quantities and nominal properties
Ordering and category labels do not justify ordinary arithmetic.
Key knowledge
An ordinal quantity can be ranked by magnitude under a stated procedure but has no meaningful algebraic operations on that scale. A nominal property assigns categories without quantity magnitude. Numeric category codes are therefore labels, not automatically quantities, while a numerical ordinal scale supports ordering without automatically supporting differences, ratios or averages.
Conditions and scope
- Distinguish the representation from the underlying property and its measurement procedure.
- A separate interval/ratio model can justify additional operations only when its assumptions are established; an arbitrary numerical recoding does not establish that model.
Sources · 3
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
- International Vocabulary of Metrology (VIM3)Joint Committee for Guides in Metrology (JCGM)Reference guideVIM3, entry 1.26VIM3, entry 1.27VIM3, entry 1.30
Evidence and review
Read VIM1.26 ordinal-quantity definition/notes,1.27 quantity-value-scale definition and1.30 nominal-property definition/examples. Do not repeat the source annotation’s problematic Richter-scale example: logarithmic magnitude differences have a specified physical interpretation.
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- foundation-measurement-ordinal-nominal-scales
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- foundations-refresh.1
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