I worked with a research company and we did surveys that involved knocking on doors and convincing people to take the survey. the names were chosen by some formula that I do not know. the point is when they sent me into an area and I had gotten all the people that would voluntarily do the survey, they would send me to a different area and send someone else to the area I just worked. It seems different people could get survey's answered by different survey takers. I know it seems strange, but it worked for the company I worked for.