A feasibility study of on-the-fly item generation in adaptive testing

The goal of this study was to assess the feasibility of an approach to adaptive testing using item models based on the quantitative section of the Graduate Record Examination (GRE) test. An item model is a means of generating items that are isomorphic, that is, equivalent in content and equivalent psychometrically. Item models, like items, are calibrated by fitting an IRT response model. The resulting set of parameter estimates is imputed to all the items generated by the model. An on-thefly adaptive test tailors the test to examinees and presents instances of an item model rather than independently developed items. A simulation study was designed to explore the effect an on-the-fly test design would have on score precision and bias as a function of the level of item model isomorphicity In addition, two types of experimental tests were administered – an experimental, on-thefly, adaptive quantitative-reasoning test as well as an experimental quantitative-reasoning linear test consisting of items based on item models. Results of the simulation study showed that under different levels of isomorphicity, there was no bias, but precision of measurement was eroded at some level. However, the comparison of experimental, on-the-fly adaptive test scores with the GRE test scores closely matched the test-retest correlation observed under operational conditions. Analyses of item functioning on the experimental linear test forms suggested that a high level of isomorphicity across items within models was achieved. The current study provides a promising first step toward significant cost reduction and theoretical improvement in test creation methodology for educational assessmen