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	Sviluppo di Scale Politomiche	Teoria della Generalizzabilità (G-Theory)
Campo	Psicometria	Psicometria
Famiglia	Latent structure	Latent structure
Anno di origine	1969–1982	1963–1972
Ideatore	Samejima, F.; Masters, G. N. (independently)	Lee J. Cronbach, Goldine Gleser, Harinder Nanda, Nageswari Rajaratnam
Tipo	Psychometric scale construction	Variance-components reliability model
Fonte seminale	Embretson, S. E. & Reise, S. P. (2000). Item Response Theory for Psychologists. Lawrence Erlbaum Associates. ISBN: 978-0805828191	Cronbach, L. J., Gleser, G. C., Nanda, H. & Rajaratnam, N. (1972). The Dependability of Behavioral Measurements: Theory of Generalizability for Scores and Profiles. Wiley.
Alias	polytomous item development, ordered-category scale construction, rating scale development, multi-category item development	G-theory, G-study / D-study framework, variance components reliability
Correlati	6	4
Sintesi	Polytomous scale development is the systematic construction and validation of measurement instruments whose items have three or more ordered response categories — such as Likert-type, rating, or partial-credit items. It applies polytomous item response theory models or ordinal factor analysis methods to evaluate item quality, estimate latent trait levels, and build a psychometrically sound scale.	Generalizability Theory is a psychometric framework that decomposes observed score variance into multiple sources — persons, items, raters, occasions, and their interactions — using analysis of variance. It replaces the single reliability coefficient of classical test theory with a family of coefficients that tell researchers how well scores generalize across different measurement conditions.