Establishing measurement equivalence is important because inaccurate assessment may lead to incorrect estimates of effects in research, and to suboptimal decisions at the individual, clinical level.

Background The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) is a widely used patient reported outcome in osteoarthritis. An important, but frequently overlooked, aspect of ...

Exact nonparametric procedures have been used to identify the level of differential item functioning (DIF) in binary items. This study explored the use of exact DIF procedures with items scored on a ...

When contextual features of test-taking environments differentially affect item responding for different test-takers and these features vary across test administrations, they may cause differential ...