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Scaling Performance Assessments: A Comparison of One‐Parameter and Two‐Parameter Partial Credit Models
Author(s) -
Fitzpatrick Anne R.,
Link Valerie B.,
Yen Wendy M.,
Burket George R.,
Ito Kyoko,
Sykes Robert C.
Publication year - 1996
Publication title -
journal of educational measurement
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.917
H-Index - 47
eISSN - 1745-3984
pISSN - 0022-0655
DOI - 10.1111/j.1745-3984.1996.tb00494.x
Subject(s) - scaling , model parameter , statistics , logistic regression , mathematics , shape parameter , item response theory , econometrics , polytomous rasch model , computer science , psychometrics , geometry
In one study, parameters were estimated for constructed‐response (CR) items in 8 tests from 4 operational testing programs using the l‐parameter and 2‐ parameter partial credit (IPPC and 2PPC) models. Where multiple‐choice (MC) items were present, these models were combined with the 1‐parameter and 3‐parameter logistic (IPL and 3PL) models, respectively. We found that item fit was better when the 2PPC model was used alone or with the 3PL model. Also, the slopes of the CR and MC items were found to differ substantially. In a second study, item parameter estimates produced using the IPL‐IPPC and 3PL‐2PPC model combinations were evaluated for fit to simulated data generated using true parameters known to fit one model combination or ttle other. The results suggested that the more flexible 3PL‐2PPC model combination would produce better item fit than the IPL‐1PPC combination.