A study of pre-equating based on item response theory

The study reports a feasibility study using item response theory (IRT) as a means of equating the Test of Standard Written English (TSWE). The study focused on the possibility of pre-equating, that is, deriving the equating transformation prior to the final administration of the test. The three-parameter logistic model was postulated as the response model and its fit was assessed at the item, subscore, and total score level. Minor problems were found at each of these levels; but, on the whole, the three-parameter model was found to portray the data well. The adequacy of the equating provided by IRT procedures was investigated in two TSWE forms. It was concluded that pre-equating does not appear to present problems beyond those inherent to IRT-equating