An Integrated Approach to Bias in the Spanish Version of the General Health Questionnaire (GHQ-12)

The aim of the paper is to illustrate a comprehensive approach to bias in an application of the General Health Questionnaire (GHQ-12) among native Spanish people and immigrants in Spain. A comprehensive evaluation of bias can detect combined effects of different types of bias and their causes. The GHQ-12, administered as part of the 2006 Spanish National Health Survey, was used for evaluating bias. The entire sample of 1,251 participants was composed of Spanish and immigrants from Morocco, Ecuador, Romania, and Colombia. Construct, method, and items bias were evaluated, using analyses of measurement invariance, response styles, and Differential Item Functioning (DIF), respectively. Integrating the results of the bias analyses, we found that the presence of bias was related to items asking about symptoms, notably dealing with feelings and personal perceptions. Furthermore, colloquialisms in the items led to bias in the comparison of Spanish speakers from Spain and South America (all of whom had Spanish as mother tongue). The comprehensive approach to bias showed the value of examining various forms of bias in an integrated manner.