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To assess how a public decision can affect citizens'interests, we need to estimate individual preferences. Economists usually assess individual preference through a market decision. Most often, however, public decisions have an impact on non-market goods. Without a market to refer to, evaluating a public decision's effect on individual welfare poses a methodological challenge. Despite major improvements, preference studies based on hypothetical questions for example, using a survey or contingent valuation are biased. The experimental methodology is a promising alternative for directly obtaining an individual valuation of a public decision. Indeed, the use of the experimental method in preference studies is growing, and our paper discusses this approach. In particular, we answer the following questions: Why is it worth using the experimental method to evaluate individual preference? And how should we conduct this kind of experiment?