Child development specialists have observed that adolescents who receive large weekly allowances tend to spend money on items considered frivolous by their parents whereas adolescents who receive small weekly allowances do not. Thus, in order to ensure that their children do not spend money on frivolous items, parents should not give their children large weekly allowances. Which of the following pieces of information would be most useful in evaluating the validity of the conclusion above? ['The percentage of adolescents who receive no weekly allowance', 'Any differences among parents in the standard used to judge an item as frivolous', 'The educational background of the child development specialists who made this observation', 'The average amount of money received by adolescents who receive large weekly allowances']