Somers' D as an Alternative for the Item-Test and Item-Rest Correlation Coefficients in the Educational Measurement Settings

Autor/in	Metsämuuronen, Jari
Titel	Somers' D as an Alternative for the Item-Test and Item-Rest Correlation Coefficients in the Educational Measurement Settings
Quelle	In: International Journal of Educational Methodology, 6 (2020) 1, S.207-221 (15 Seiten)Infoseite zur Zeitschrift PDF als Volltext kostenfreie Datei Verfügbarkeit
Sprache	englisch
Dokumenttyp	gedruckt; online; Zeitschriftenaufsatz
ISSN	2469-9632
Schlagwörter	Correlation; Test Items; Scores; Difficulty Level; Statistical Analysis; Test Reliability; Educational Testing + Suchen Sie Ihr Suchwort? Korrelation; Test content; Testaufgabe; Schwierigkeitsgrad; Statistische Analyse; Testreliabilität
Abstract	Pearson product-moment correlation coefficient between item g and test score X, known as item-test or item-total correlation ("Rit"), and item-rest correlation ("Rir") are two of the most used classical estimators for item discrimination power (IDP). Both "Rit" and "Rir" underestimate IDP caused by the mismatch of the scales of the item and the score. Underestimation of IDP may be drastic when the difficulty level of the item is extreme. Based on a simulation, in a binary dataset, a good alternative for "Rit" and "Rir" could be the Somers' "D": it reaches the ultimate values +1 and -1, it underestimates IDP remarkably less than "Rit" and "Rir", and, being a robust statistic, it is more stable against the changes in the data structure. Somers' "D" has, however, one major disadvantage in a polytomous case: it tends to underestimate the magnitude of the association of item and score more than "Rit" does when the item scale has four categories or more. (As Provided).
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Erfasst von	ERIC (Education Resources Information Center), Washington, DC
Update	2024/1/01