Towards a theory of bias and equivalence

Abstract

"Bias refers to the presence of nuisance factors in cross-cultural research. Three types of bias are distinguished, depending on whether the nuisance factor is located at the level of the construct (construct bias), the measurement instrument as a whole (method bias) or the items (item bias or differential item functioning). Equivalence refers to the measurement level characteristics that apply to cross-cultural score comparisons; three types of equivalence are defined: construct (identity of constructs across cultures), measurement unit (identity of measurement unit), and scalar equivalence (identity of measurement unit and scale origin). Bias often jeopardizes equivalence. Implications of the occurrence of bias on equivalence are described. Examples of how equivalence can be enhanced in multilingual studies are given." (author's abstract)