Sound, informed item selection and revision decisions are made based on information collected during the field tests. One process conducted during this phase is a differential item functioning analysis for various subgroups, such as race, ethnicity, and gender. This is done in order to determine if the items are behaving differentially for students that have comparable abilities. If a reason is found for the differential functioning, the item is eliminated. It is rare, however, that an item is excluded for this reason.