Can there possibly be a methodology that is 100% correct? If you try to interview 100% of people, then the results will be out of date by the time you've reach

Can there possibly be a methodology that is 100% correct? If you try to interview 100% of people, then the results will be out of date by the time you've reached everybody. (Plus the Hawthorne effect suggests people will start changing their answers as people comment on the questions they are asked.) So you create samples, and necessarily some of those samples will be unrepresentative because they will miss some nuance. Catch 22 - unless you interview 100% of the people, you can't know what all the nuances are. I guess the best we can hope for is a result that merges lots of different results using lots of different methodologies, and base decisions on that.