Although focus groups are being used increasingly by survey and market researchers who are developing questionnaires, research to evaluate focus group methodology is scant and the social psychological dimensions of focus group processes are insufficiently examined.
Bischoping, K., and J. Dykema. Toward a Social Psychological Programme for Improving Focus Group Methods of Developing Questionnaires. Vol. 15, no. 4, Journal of Official Statistics, 1999, pp. 495-16.