Put 15 people in your staged look up group, and the number of passers by will likely jump to 40 percent. The more people who you have agreeing with you the more people there are that will agree with you. Liking People are inclined to agree with people they like. Tupperware Corporation knows that. Thus the potential hostess invites her friends first.
Friends are more likely to buy.
Car sales is also a proving case. The salesman is your friend and the sales manager is your enemy. Your friend can go argue with the sales manager for a better price on your behalf. Lo and behold the hook is set in your wallet. Rest assured the salesman knows the answer before he asks the question.