There are several issues to consider when evaluating study quality , including but not limited to 1 ) whether the sample estimates of WTP are representative of the population WTP ; 2 ) whether the good to be valued is comprehended and accepted by the respondent ; 3 ) whether the WTP elicitation format is designed to minimize strategic responses ; 4 ) whether WTP is sensitive to respondent familiarity with the good , to the size of the change in the good , and to income ; 5 ) whether the estimates of WTP are broadly consistent with other estimates of WTP for similar goods ; and 6 ) the extent to which WTP responses are consistent with established economic principles .
There is only one issue to consider when evaluating study quality .