Statistics - (Scales of measurement|Type of variables)

Thomas Bayes


According to Stevens theory (On the Theory of Scales of Measurement), the four scales of measurement are:

  • nominal
  • ordinal
  • interval
  • ratio

Each of these four levels refers to the relationship between the values of the variable.

It is also helpful to think of the scales of measurement as building in complexity, from the most basic (nominal) to the most complex (ratio).

Each higher level of measurement includes aspects of those before it.

Level Scale Application Basic Empirical Operations Statistics
1 Nominal Categorization Equality Number of cases , mode, Contingency correlation
2 Ordinal Order Greater or less median, percentile
3 Interval Distance Equality of difference or difference Mean, Standard deviation, Rank-order correlation, Product-moment correlation
4 Ratio Absolute zero Equality of Ratios Coefficient of variation

Table 1

Table 1 of Stevens theory (On the Theory of Scales of Measurement)

Level Of Measurement Table 1


Levels are type of measurement.


A Nominal Measurement is the type of measurement in which the values of the variable are names and not numerical at all. It' s used to assign individual cases to categories.

The Country of Origin is a nominal variable

More … Statistics - (Discrete | Nominal | Category | Reference | Taxonomy | Class | Enumerated | Factor | Qualitative | Constant ) Data


The Ordinal Measurement involves collecting information in which the order is significant and is used to rank order cases.


Interval measurements give:

  • distance between two values
  • and order (rank) between this distances


Ratio Measurement gets its name from the fact that meaningful fraction (or ratio) can be constructed with a ratio variable.

Documentation / Reference

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