The problem of obtaining designs that result in the most precise parameter estimates is encountered in at least two situations where item response theory (IRT) models are used. In so-called two-stage testing procedures, certain designs that match difficulty levels of the test items with the ability of the examinees may be located. Such designs…

Any systematic approach to the assessment of students' ability implies the use of a model. The more explicit the model is, the more its users know about what they are doing and what the consequences are. The Rasch model is a strong model where measurement is a bonus of the model itself. It is based on four ideas: (1) separation of observable…