Box 1.

What is a discrete choice experiment?

A discrete choice experiment (DCE) is a technique for eliciting preferences that provides information about the way individuals value different attributes of health, as well as the potential demand for new programmes, services, or treatments. DCEs are based on the assumption that healthcare interventions/services can be described by their characteristics (or attributes), and that an individual’s valuation depends on the levels of the attributes. It is also assumed that individuals behave rationally and make choices that maximise their satisfaction (or utility in economics terminology). In a DCE participants are presented with a series of questions where they are asked to choose between hypothetical alternatives, each with differing levels of the attributes being tested. In the example below an individual is asked to choose between two chocolate bars (A and B), which are described by five attributes (cocoa content, price, size and so on. Each attribute will have a number of potential options or levels.
Which chocolate bar would you prefer?
	Chocolate bar A	Chocolate bar B
Cocoa content	25% (milk chocolate)	60% (dark chocolate)
Added ingredients	Almonds, raisins	None
Fairtrade?	No	Yes
Size	60 g	75 g
Cost	£1.00	£1.25
I would prefer: Chocolate bar A Chocolate bar B Neither By asking a number of questions in which the levels of the attributes are different, a picture of the strength of preferences for each attribute and level can be built. One is able to investigate the importance that individuals place on different aspects of a product/service, and the extent to which they are willing to make trade-offs between those aspects; for example, the increase/decrease in cost related to the chocolate bar being Fairtrade. When costs are included, DCEs can estimate the ‘willingness-to-pay’ of particular product/services/changes in attributes. The information from a DCE can be used to infer what is important to individuals when making choices in health. It is also possible to estimate the likelihood that individuals would choose a new service and their willingness to pay; vital information when commissioning new services.