Detection of advance item knowledge using response times in computer adaptive testing

We propose a new method for detecting item preknowledge in a CAT based on an estimate of “effective response time” for each item. Effective response time is defined as the time required for an individual examinee to answer an item correctly. An unusually short response time relative to the expected effective response time may be an indicator of item preknowledge. The new method was applied to empirical data. Results showed that the Type I error rate of the statistic can be controlled. Power analysis revealed that the power is high when the response time is reduced even for a small set of items where the examinee has item preknowledge.