Theory precedes measurement

"In text books, the numbers that result from measurements usually appear as the archetypes of the `irreducible and stubborn facts' to which the scientist must, by struggle, make his theories conform. But in scientific practice, as seen through the journal literature, the scientist often seems rather to be struggling with the facts, trying to force them to conformity with a theory he does not doubt. Quantitative facts cease to seem simply the `given'. They must be fought for and with, and in this fight the theory with which they are to be compared proves the most potent weapon."

"Often scientists cannot get numbers that compare well with theory until they know what numbers they should be making nature yield... To the extent that measurement and quantitative technique play an especially significant role in scientific discovery, they do so precisely because, by displaying serious anomaly, they tell scientists when and where to look for a new qualitative phenomenon... The road from scientific law to scientific measurement can rarely be traveled in the reverse direction." (Thomas Kuhn, 1961, p.193-219, emphasis his).

It is this almost impassable road from "measurement" to law that social scientists attempt to travel by modeling available data - that is, by trying to find models that will account for the data as they appear. In this relentless pursuit, the social scientist bypasses one of the main functions of scientific measurement, the identification of anomalies.

David Andrich
Murdoch University, Australia

"Scientific truths, of whatever order, are reached by eliminating perturbing or conflicting factors, and recognizing only fundamental factors."
Herbert Spencer (1879) The Data of Ethics

"A hypothesis has met its supreme test when it solves not only the problem it was designed to cover, but also the cognate problems that arise during further investigation."
Odell Shepard (1923) "A Youth to Fortune and to Fame Unknown", Modern Philology, 20, 372

Hence the success of Newton and Rasch, and the failure of Ptolemy of Alexandria and the proponents of ordinal measurement.

Theory precedes measurement.Andrich D.A. … Rasch Measurement Transactions, 1998, 12:2 p. 627-9.

Rasch Publications
Rasch Measurement Transactions (free, online)	Rasch Measurement research papers (free, online)	Probabilistic Models for Some Intelligence and Attainment Tests, Georg Rasch	Applying the Rasch Model 3rd. Ed., Bond & Fox	Best Test Design, Wright & Stone
Rating Scale Analysis, Wright & Masters	Introduction to Rasch Measurement, E. Smith & R. Smith	Introduction to Many-Facet Rasch Measurement, Thomas Eckes	Invariant Measurement: Using Rasch Models in the Social, Behavioral, and Health Sciences, George Engelhard, Jr.	Statistical Analyses for Language Testers, Rita Green
Rasch Models: Foundations, Recent Developments, and Applications, Fischer & Molenaar	Journal of Applied Measurement	Rasch models for measurement, David Andrich	Constructing Measures, Mark Wilson	Rasch Analysis in the Human Sciences, Boone, Stave, Yale
in Spanish:	Análisis de Rasch para todos, Agustín Tristán		Mediciones, Posicionamientos y Diagnósticos Competitivos, Juan Ramón Oreja Rodríguez

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