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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.
For example, both 1 ⁄ 2 inch and 15 millimetres (0.59 in) copper pipe is actually the same pipe which has a nominal internal diameter of 1 ⁄ 2 an inch and a nominal external diameter of 15 millimetres [6] (diameter is always internal in the imperial measurement system and always external in metric).
For example, a scaling technique might involve estimating individuals' levels of extraversion, or the perceived quality of products. Certain methods of scaling permit estimation of magnitudes on a continuum, while other methods provide only for relative ordering of the entities. The level of measurement is the type of data that is measured.
A nominal variable, or nominal group, is a group of objects or ideas collectively grouped by a particular qualitative characteristic. [3] Nominal variables do not have a natural order, which means that statistical analyses of these variables will always produce the same results, regardless of the order in which the data is presented. [1] [3]
Various attempts have been made to produce a taxonomy of levels of measurement. The psychophysicist Stanley Smith Stevens defined nominal, ordinal, interval, and ratio scales. Nominal measurements do not have meaningful rank order among values, and permit any one-to-one (injective) transformation.
Typologies are used in both qualitative and quantitative research. An example of a typology would be classification such as by age and health: young-healthy, young-sick, old-healthy, old-sick. Typological theorizing is the development of theories about configurations of variables that constitute theoretical types. [ 2 ]
Measurement involving ambiguity in characteristics of interest in the rating target are generally improved with multiple trained raters. Such measurement tasks often involve subjective judgment of quality. Examples include ratings of physician 'bedside manner', evaluation of witness credibility by a jury, and presentation skill of a speaker.
This is a list of statistical procedures which can be used for the analysis of categorical data, also known as data on the nominal scale and as categorical variables. General tests [ edit ]