Comparing single-pool and multiple-pool designs regarding test security in computerized testing

This article compares the use of single- and multiple-item pools with respect to test security against item sharing among some examinees in computerized testing. A simulation study was conducted to make a comparison among different pool designs using the item selection method of maximum item information with the Sympson-Hetter exposure control and content balance. The results from the simulation study indicate that two-pool designs have a better degree of resistance to item sharing than do the single-pool design in terms of measurement precision in ability estimation. This article further characterizes the conditions under which employing a multiple-pool design is better than using a single, whole pool in terms of minimizing the number of compromised items encountered by examinees under a randomized item selection method. Although no current computerized testing program endorses the randomized item selection method, the results derived in this study can shed some light on item pool designs regarding test security for all item selection algorithms, especially those that try to equalize or balance item exposure rates by employing a randomized item selection method locally, such as the a-stratified-with-b-blocking method.