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ERIC Number: EJ856068
Record Type: Journal
Publication Date: 2009
Pages: 14
Abstractor: As Provided
Reference Count: 5
ISSN: ISSN-1536-6367
On Interpreting the Model Parameters for the Three Parameter Logistic Model
Maris, Gunter; Bechger, Timo
Measurement: Interdisciplinary Research and Perspectives, v7 n2 p75-88 2009
This paper addresses two problems relating to the interpretability of the model parameters in the three parameter logistic model. First, it is shown that if the values of the discrimination parameters are all the same, the remaining parameters are nonidentifiable in a nontrivial way that involves not only ability and item difficulty, but also the guessing parameters. Second, a situation is considered where different researchers analyze the same test with different instances of the three parameter logistic model. One researcher reaches the conclusion that students guess, whereas the other one concludes that students do not guess. Both examples illustrate the many-one relation between statistical models and the probability distributions they imply, which is the overarching topic of this paper. (Contains 3 figures and 2 tables.)
Psychology Press. Available from: Taylor & Francis, Ltd. 325 Chestnut Street Suite 800, Philadelphia, PA 19106. Tel: 800-354-1420; Fax: 215-625-2940; Web site:
Publication Type: Journal Articles; Reports - Research
Education Level: N/A
Audience: N/A
Language: English
Sponsor: N/A
Authoring Institution: N/A