Designs with Ordered Attributes
Discrete choice experiments often, if not usually, have economic attributes; that is, attributes that have ordered levels with associated benets or costs that monotonically increase with level. Examples include volume, performance measures, and even quality indices. Benets typically are assumed to increase at a decreasing rate and costs increase at an increasing rate with increasing attribute level. Partworths are assumed to monotonically increase with benets. Partworths associated with price levels are assumed to monotonically decrease with increasing price level. In the case of individual choice theory that underlies discrete choice experimentation (DCE), it is assumed that there are incremental benets gained or costs incurred in choosing one prole over another. Decision makers will choose to reduce levels of one attribute to increase levels of another if the incremental gain of switching more than offsets the incremental loss. Clearly, attributes must be ordered for the notions of reducing and increasing attribute levels to make sense.