Multidimensional scaling as a tool for analysing quality of life data.

Multidimensional scaling (MDS) is introduced and discussed as a graphical method to complement conventional descriptive and confirmatory methods in the validation and analysis of quality of life (QOL) data. An outline of M DS as a statistical technique is given, and its application in the context of QOL research is described. The use of MDS is then illustrated in an example based on a study of 300 cancer survivors who completed the functional assessment of cancer therapy-general (FACT-G) and the EORTC core quality of life questionnaire (QLQ-C30). The correlational structure of the two widely used QOL instruments is investigated by means of MDS, and differences between the two questionnaires are elaborated. Finally, the merits and drawbacks of MDS are discussed in the specific context of the example and in the general framework of QOL research.