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Using Testlet Response Theory to Examine Local Dependence in C-Tests

September, 2015

Article Type: Research Article

Journal Name: Applied Measurement in Education

DOI: 10.1080/08957347.2014.1002919 move

Issue: | Volume: 28 | Page No:


C-tests are gap-filling tests widely used to assess general language proficiency for purposes of place-ment, screening, or provision of feedback to language learners. C -tests consist of several short texts in which parts of words are missing. We addressed the issue of local dependence in C-tests using an explicit modeling approach based on testlet response theory. Data were provided by a total sample of 4,708 participants working on eight C-test texts with 20 gaps each. The resulting parameter estimates were compared to those obtained from (a) a polytomous item response theory (IRT) model and (b) a standard IRT model that ignored the dependence s tructure. Testlet effects proved to be very s mall and correspondence between parameters obtained from the different modeling approaches was high. When local dependence was ignored reliability of the C -test was slightly overestimated. Implications for the analysis of testlets in general, and C -tests in particular are discussed.