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A new approach to test score equating using item response theory with fixed C-parameters

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Abstract

Because parameter estimates from different calibration runs under the IRT model are linearly related, a linear equation can convert IRT parameter estimates onto another scale metric without changing the probability of a correct response (Kolen & Brennan, 1995, 2004). This study was designed to explore a new approach to finding a linear equation by fixing C-parameters for anchor items in IRT equating. A rationale for fixing C-parameters for anchor items in IRT equating can be established from the fact that the C-parameters are not affected by any linear transformation. This new approach can avoid the difficulty in getting accurate C-parameters for anchor items embedded in the application of the IRT model. Based upon our findings in this study, we would recommend using the new approach to fix C-parameters for anchor items in IRT equating.

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Correspondence to Guemin Lee.

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This work was supported by a Korea Research Foundation Grant funded by the Korean Government (MOEHRD, Basic Research

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Lee, G., Fitzpatrick, A.R. A new approach to test score equating using item response theory with fixed C-parameters. Asia Pacific Educ. Rev. 9, 248–261 (2008). https://doi.org/10.1007/BF03026714

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  • DOI: https://doi.org/10.1007/BF03026714

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