What are the requirements for the use of anchoring vignettes?

We define two key requirements for the use of vignettes as:

1. Response consistency, which requires that each individual uses the response categories for the self-assessment question in approximately the same way that he or she uses them to evaluate hypothetical scenarios in the vignettes. Different individuals may use the categories in different ways.

2. Vignette equivalence, which required that the domain levels represented in each vignette are understood in the same way on average by all respondents. Of course, even when respondents understand vignettes in the same way, different respondents may use the categorical responses in different ways in answering questions about the vignettes. Each respondent can still apply different types of DIF.