Why are we weighting? The role of importance ratings in quality of life measurement

Many Quality of Life (QoL) instruments ask respondents to rate a number of life domains in terms of satisfaction and personal importance, and derive w eighted satisfaction scores by multiplying the two ratings. This paper demo nstrates that this practice is both undesirable and unnecessary. QoL domain s are selected on the basis of their inherent importance, rendering separat e importance rating partially redundant. Weighted scores present difficulti es in interpretation. Further, we show that multiplicative composites have undesirable psychometric properties. There is evidence that multiplicative composites have little or no advantage over unweighted ratings in correlati onal or predictive studies. Apart from the face validity and the intuitive appeal of multiplying satisfaction ratings by importance ratings, there app ear to be no sound reasons for doing so, and several good reasons not to do so.