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	Alpha di Cronbach longitudinale	Teoria della Generalizzabilità (G-Theory)
Campo	Psicometria	Psicometria
Famiglia	Latent structure	Latent structure
Anno di origine	1951 (alpha); longitudinal application systematised ca. 1990s–2000s	1963–1972
Ideatore	Lee J. Cronbach (alpha); longitudinal extension formalised in scale validation literature from 1980s onward	Lee J. Cronbach, Goldine Gleser, Harinder Nanda, Nageswari Rajaratnam
Tipo	Reliability estimation across time	Variance-components reliability model
Fonte seminale	Cronbach, L. J. (1951). Coefficient alpha and the internal structure of tests. Psychometrika, 16(3), 297–334.	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	repeated-measures alpha, longitudinal internal consistency, wave-specific Cronbach's alpha, time-point reliability estimation	G-theory, G-study / D-study framework, variance components reliability
Correlati	4	4
Sintesi	Longitudinal Cronbach's alpha assesses the internal consistency reliability of a scale at each wave of a repeated-measures study and examines whether that reliability remains stable across time. It is an essential step in longitudinal scale validation, ensuring that a scale measures its construct with consistent precision at every measurement occasion.	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.