Detecting Fraudulent Erasures at an Aggregate Level

Wollack, Cohen, and Eckerly suggested the “erasure detection index” (EDI) to detect fraudulent erasures for individual examinees. Wollack and Eckerly extended the EDI to detect fraudulent erasures at the group level. The EDI at the group level was found to be slightly conservative. This article suggests two modifications of the EDI for the group level. The asymptotic null distribution of the two modified indices is proved to be the standard normal distribution. In a simulation study, the modified indices are shown to have Type I error rates close to the nominal level and larger power than the index of Wollack and Eckerly. A real data example is also included