השוואת שיטות

	פונקציונליות פריט דיפרנציאלית אורכית (Longitudinal DIF)	תיאוריית תגובת פריט (IRT)
תחום	פסיכומטריה	פסיכומטריה
משפחה	Latent structure	Latent structure
שנת המקור	1980s–2000s	1952–1968
הוגה השיטה	Multiple contributors; foundational DIF methods by Lord (1980) extended to longitudinal designs	Frederic M. Lord (and Allan Birnbaum for the 2PL/3PL models)
סוג	Item-level bias detection across time	Probabilistic measurement model
מקור מכונן	Millsap, R. E., & Kwok, O. M. (2004). Evaluating the impact of partial factorial measurement invariance on selection in two groups. Psychological Methods, 9(1), 93–115.	Lord, F. M. & Novick, M. R. (1968). Statistical Theories of Mental Test Scores. Addison-Wesley.
כינויים	longitudinal DIF, DIF across time, temporal DIF, longitudinal item bias	IRT, latent trait theory, item characteristic curve theory, modern test theory
קשורות	6	5
תקציר	Longitudinal differential item functioning detects whether individual test or scale items behave differently across measurement occasions for the same respondents. It extends standard DIF methodology to repeated-measures designs, ensuring that observed change scores genuinely reflect construct change rather than shifts in item characteristics over time.	Item response theory models the probability that a respondent answers an item correctly (or endorses it) as a function of the respondent's latent trait level and the item's own statistical properties — difficulty, discrimination, and guessing. Unlike classical test theory, IRT places persons and items on the same scale, yielding measurement that is sample-independent for items and test-independent for persons.