ERIC Number: ED395024
Record Type: RIE
Publication Date: 1991-Feb
Reference Count: N/A
An Investigation of the Use of Simplified IRT Models for Scaling and Equating the TOEFL Test. TOEFL Technical Report TR-2.
Way, Walter D.; Reese, Clyde M.
The use of two alternative item response theory (IRT) estimation models in the scaling and equating of the Test of English as a Foreign Language (TOEFL) was explored; and item scaling and test equating results based on these models were compared with results based on the three-parameter (3PL) model currently being used with the TOEFL. Models were a modified one-parameter (M1PL) and a modified two-parameter (M2PL). Simulated equatings were compared in terms of correlations between estimated and generating parameters, model-data fit, and concordance of simulated score conversions, with conversions based on the generating parameters. Results clearly indicated that the 3PL model performed better than the M1PL and M2PL models. There was also evidence that the M2PL model performed better than the M1PL. Discrepancies between score conversions based on the M1PL and the M2PL models and those based on the 3PL model tended to occur at the lower and upper ends of the score scales. Results of the study for the 3PL model indicated that while correlations between item parameter estimates and generating parameters tended to be affected by sample size, neither the quality of model-data fit nor the quality of simulated equatings was sensitive to sample size. Three appendixes present the raw-to-scaled score conversions for three TOEFL sections. (Contains 3 figures, 8 tables, 12 appendix tables, and 16 references.) (Author/SLD)
Publication Type: Reports - Evaluative
Education Level: N/A
Authoring Institution: Educational Testing Service, Princeton, NJ.
Identifiers: Item Parameters; One Parameter Model; Test of English as a Foreign Language; Three Parameter Model; Two Parameter Model