Title: The impact of the difficulty level of compromised common items on IRT scaling and equating under the common item equating design

Authors: Moatasim A. Barri

Addresses: Department of Curriculum and Teaching, Taibah University, Medina, Saudi Arabia

Abstract: The common item equating design requires two forms of a test which have a set of items in common in order to control for differences in examinee ability. The common set is subject to compromise when it is used repeatedly, which most likely becomes a serious threat to test fairness. If cheating occurs on common items, the equating process produces inaccurate results which might vary as a result of common item difficulty. This simulation study was conducted to evaluate the impact of the difficulty level of compromised common items on the equating process. The recovery of scaling coefficients and equated scores was assessed using bias and RMSE under various cheating conditions. The results indicated that cheating on higher-difficulty common items produced the most overestimation in the scaling coefficients; which, in turn, caused the most inflation in equating true scores for all test takers, whether they engage in cheating or not.

Keywords: item response theory; linking; equating; common items; test compromise.

DOI: 10.1504/IJQRE.2021.119805

International Journal of Quantitative Research in Education, 2021 Vol.5 No.3, pp.223 - 243

Received: 04 May 2019
Accepted: 05 May 2020
Published online: 21 Dec 2021 *

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