These judgments are difficult to make, so that various simplifying procedures may be used in administering the scaling task, including the time trade-off technique (50; 55, p36; 73). Methods such as “willingness to pay” or the “time trade-off” are alternative ways to present the standard gamble, rather than different methods. As before, the judges are asked to imagine that they are suffering from the condition whose severity is to be rated. They are asked to choose between remaining in that state for the rest of their natural lifespan (e.g., 30 years for a 40 year-old person), or returning to perfect health for fewer years. The number of years of life expectancy they would sacrifice to regain full health indicates how severely the condition is rated. The utility for the person with 30 years of life expectancy would be given as
Utility = (30 −Years traded)/30.