Many test developers try to ensure the content validity of their tests by having external experts review the items, e.g. in terms of relevance, difficulty, or clarity. Although this approach is widely accepted, a closer look reveals several pitfalls need to be avoided if experts' advice is to be truly helpful. The purpose of this paper is to…

This focus article provided the author with an opportunity to unpack the consensus definition of validity and to explore its implications in the light of recent debates. He proposed an elaboration of the consensus definition, which was intended to express the spirit of the "Standards for Educational and Psychological Testing" with increased…