This paper discusses basic issues about the nature of measurement for concepts in the social sciences and medicine, introducing a three-stage theory of measurement. In science and policy investigations we study quantities and qualities (or quality/quantity concepts)1 and their relations in order to understand and predict the behavior of individuals/tokens displaying those quantities or falling under those concepts. What does it mean to measure a quantity (e.g. body size) or to assign a concept or category (e.g. ‘underweight’) to a token? In medicine, as throughout natural and social science, measurement is not just assigning categories or numbers; it is assigning values in a systematic and grounded way. This involves applying some well-grounded metric representing the quantity (e.g. body mass index (BMI)) to the token.
Cartwright, N., Bradburn, N. M., & Fuller, J. (2016). A Theory of Measurement