Many testing programs include a section of optional questions in addition to mandatory parts of a test. These optional parts of a test are not often truly parallel to one another, and groups of examinees selecting each optional test section are not equivalent to one another. This paper provides a general method based on missing-data methods for…

Item parameter estimates derived through item response theory methods have been considered relatively robust to changes in item position and context, but the anomaly in reading scores from the 1986 National Assessment of Educational Progress (NAEP) illustrates problems with common population equating procedures when there are test form changes.…