You usually need to meet certain criteria to be eligible and participants may fudge their answers to participate. I’ve done food testing on and off through the years and you always need to answer some questions beforehand to determine eligibility. If you gave a “wrong” answer, the survey-asker would say something like “Are you sure?”, prompting you to pick the other choice that made you eligible for the study. Or even without prompting, if I’m trying to get paid to taste bubblegum and they ask how often you have bubblegum, I’m more likely to inflate my reported frequency compared to my actual frequency of gum chewing.