The issue of equity and the need for testing accommodations goes directly to the heart of comparable construct validity and the fairness of the testing process. It is important to distinguish two kinds of comparability. One, called score comparability, means that the properties of scores, such as reliabilities, internal patterns of relationships between items, and external relationships with other variables, are comparable across groups and settings. Score comparability is important in justifying uniform score interpretation and use for different groups and in different circumstances.
The other kind, called task comparability, means that the tested task elicits the same cognitive processes across different groups and different circumstances. Within task comparability, two types of processes may be distinguished: those that are relevant to the construct measured and those that are ancillary to the construct but nonetheless involved in task performance. Comparability of construct-relevant processes is necessary to sustain common score meaning across groups and contexts.
Ancillary processes may be modified without jeopardizing score meaning. This provides a fair and legitimate basis for accommodating tests to the needs of students with disabilities and those who are English-language learners (Willingham et al., 1988). For example, a fair accommodation might be to read a mathematics test aloud to a student with certain disabilities, because reading is ancillary to the construct being measured (mathematics), whereas it would not be fair to read a reading test aloud. The availability of multimedia test presentation and response modes on computers promises an accommodation to serve the needs of certain students with disabilities, such as visually impaired and hearing-impaired students (Bennett, 1998).
Thus, comparable validity—and test fairness—do not require identical task conditions, but rather common construct-relevant processes, with ignorable construct-irrelevant or ancillary processes that may be different across individuals and groups. Such accommodations, of course, have to be justified with evidence that score meaning and properties have not been unduly eroded in the process.
Fairness, like validity, cannot be properly addressed as an afterthought once the test has been developed, administered, and used. It must be confronted throughout the interconnected phases of the testing process,