> For the complete documentation index, see [llms.txt](https://mandober.gitbook.io/math-debrief/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://mandober.gitbook.io/math-debrief/100-fundamentals/terms/level-of-measurement.md).

# Level of measurement

<https://en.wikipedia.org/wiki/Level_of_measurement>

*Level of measurement* or *scale of measure* is a classification that describes the nature of information within the values assigned to variables.

Psychologist Stanley Smith Stevens developed the best-known classification with 4 levels (or scales) of measurement: nominal, ordinal, interval, and ratio.

Stevens claimed that all measurement in science was conducted using 4 different types of scales that he named nominal, ordinal, interval and ratio, unifying both qualitative (which are described by his nominal type) and quantitative (to a different degree, described by his other scales). The concept of scale types later received the mathematical rigour that it lacked at its inception.