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	Modello IRT logistico a due parametri (2PL)	Alpha di Cronbach (Analisi di Affidabilità)	Affidabilità inter-rater (kappa di Cohen e ICC)
Campo	Psicometria	Statistica	Psicometria
Famiglia	Latent structure	Latent structure	Latent structure
Anno di origine	1980	1951	1960 (kappa); 1979 (ICC)
Ideatore	Frederic M. Lord	Lee J. Cronbach	Cohen (kappa, 1960); Shrout & Fleiss (ICC, 1979)
Tipo	Item response model / latent trait model	Reliability / internal consistency coefficient	Reliability / agreement analysis
Fonte seminale	Lord, F. M. (1980). Applications of Item Response Theory to Practical Testing Problems. Erlbaum.	Cronbach, L. J. (1951). Coefficient alpha and the internal structure of tests. Psychometrika, 16(3), 297–334.	Cohen, J. (1960). A Coefficient of Agreement for Nominal Scales. Educational and Psychological Measurement, 20(1), 37–46.
Alias	two-parameter logistic model, 2PL model, 2PL IRT — İki Parametreli Madde Tepki Modeli	coefficient alpha, alpha reliability, internal consistency reliability, Güvenilirlik Analizi (Cronbach Alpha)	inter-rater reliability, interrater agreement, rater agreement, Değerlendiriciler Arası Güvenilirlik (Cohen's κ, ICC)
Correlati	6	4	6
Sintesi	The two-parameter logistic item response model, formalised by Frederic Lord (1980), describes the probability that a respondent answers a binary test item correctly as a smooth S-shaped function of the respondent's latent ability. By estimating a separate discrimination parameter for each item alongside a difficulty parameter, 2PL allows items to differ in how sharply they distinguish high- from low-ability respondents — making it the standard model for large-scale educational and psychological assessments.	Cronbach's alpha is a coefficient of internal consistency that quantifies the degree to which a set of items on a scale measures the same underlying construct. Introduced by Lee J. Cronbach in 1951, it remains the most widely reported reliability index in social-science, health, and educational research.	Interrater reliability quantifies the degree to which two or more independent raters produce consistent scores when evaluating the same individuals or products. The family encompasses Cohen's kappa, introduced in 1960 for categorical judgments, and the Intraclass Correlation Coefficient (ICC) for continuous ratings, together spanning most measurement scenarios encountered in behavioral, health, and educational research.