I was checking the answers for a quiz I'm running and came across this...
Two family teams, each with five members, would be asked to guess the results of surveys, in which 100 people would be asked open ended questions (e.g. "we asked 100 people to name something associated with the country Wales" or "we asked 100 people to name the largest breed of dog you think you could kick to death"). Although rarely acknowledged in the show, the 100 people surveyed would invariably be audience members who had volunteered prior to the show.
Bravo, very subtle.