Psychometrics can be seen as the branch of psychology concerned with the design and use of psychological tests and the application of statistical and mathematical techniques to psychological testing, but there is more...

"The change has been from functionalism to structuralism. That is, the goal of psychological theorizing has changed from explaining antecedent/consequent relationships to explaining performance from the systems and subsystems of underlying processes. [...] If the construct validation process is equivalent to theory construction, then paradigm changes should influence construct validation research as deeply as other psychological research" (Embretson (Whitely), 1983)

“The goal of the analysis of psychological data, however mathematical, is psychology, not mathematics” (Thissen and Steinberg, 1988).

“[Psychological measurement] deals with the construction of structural hypotheses rather than with inference from samples” (Guttman, 1971; Quoted in Levy, 1994).

“The main objective of psychometrics may be phrased as mathematical modeling of human behavior.” (Fumiko Samejima, 1997).

"...substantive mathematical modeling has become essential." (Fumiko Samejima, 1997).