Conjoint analysis is a technique for measuring respondent preferences about the attributes of a product or service. It is the ideal tool for new/improved product development. The choice based conjoint (CBC) analysis task asks the respondents to make choices in the same fashion as consumers normally do, by trading off features one against the other, either by ranking or choosing one of several product combinations. For example, a task could be: do you prefer a "flight that is cramped, costs £250 and has one stop" or a "flight that is spacious, costs £500 and is direct"?
Using conjoint analysis, you can determine both the relative importance of each attribute (e.g. spaciousness, price, number of stops) as well as which levels of each attribute are most preferred (e.g. how much is a price of £250 more preferred than a price of £500).