Intellectual assessment is central to the process of diagnosing an intellectual disability and the assessment process needs to be valid and reliable. One fundamental aspect of validity is that of measurement invariance, i.e. that the assessment measures the same thing in different populations. There are reasons to believe that measurement…

The 18 items' Non-Communicating Adult Pain Checklist (NCAPC) has been developed from the 27 items Non-Communicating Children Pain Checklist to better capture pain behavior of adults with Intellectual and Developmental Disabilities (IDD). As part of the NCAPC's measurement properties, internal consistency, reliability and sensitivity to pain have…