Methodology for measuring health-state preferences--II: Scaling methods.

This paper begins with a discussion of measurement principles relevant to determining health-state preferences. Six scaling methods are described and evaluated on the basis of their reliability, validity, and feasibility. They are the standard gamble, time trade-off, rating scale, magnitude estimation, equivalence, and willingness-to-pay methods. Reliability coefficients for most methods are acceptable although the low coefficients for measurements taken a year apart suggest that preferences change over time. Convergent validity among methods has been supported in some but not all studies, and there are limited data supporting hypothetical relationships between preferences and other variables. The category ratings method is easiest to administer and appears to yield valid scale values; thus, it is recommended for large-sample studies. However, decision-oriented methods, particularly the time trade-off and standard gamble, may be more effective in small-scale investigations and individual decision making.