Fig. 2

Level preference and utility. Utility quantitatively represents the relative value that the respondent attaches to each proposed level of each attribute, e.g. Quality of life is an attribute with two possible levels 'improves QoL' or 'does not improve QoL'. In this case, 'improves QoL' was deemed to be much more valuable than 'does not improve QoL' by patients. Partial utilities only make sense within the same attribute and depend on the number of proposed levels, i.e. they are relative values. The first column (% Direct choice) shows the percentage of times that each level was chosen, considering that all levels are supposed to be represented an equal number of times in the DCE. This is transformed into the level utility shown in the second column (Level utility). The relative difference in utility between 2 levels of the same attribute represents the strength of the preference for a particular level over the other