难易程度：★★★★★
题目题材：社会
gre argument 199题目：
There is a general idea that waiters and waitresses are more likely to receive larger gratuities from large groups of people. A recent research study suggests this is not true. The researchers examined the relationship between the size of tips(2) in restaurants and the number of meals(1) charged on the bill. They found that, while most tips were around 15 percent, the minimum percentage considered appropriate, people dining alone tipped consistently more (19 percent) and those dining in groups of four or more tipped considerably less (13 percent) than this 15 percent standard(3,4). These results strongly suggest that people dining in a group are less likely to feel personally responsible for leaving an adequate or generous tip(5).
提纲：
(1)The number of meals charged on the bill does not necessarily indicate the number of people dined.
(2)The argument contains no information concerning the method used by the researchers to analyze the amount of tips, thus the reliability of the result is open to doubt.
(3)The author does not inform us the total amount of money charged per person of people dining alone and those dining in groups, waiters could still receive more tips if people dinning in groups expend significantly more money per person on their meals.
(4)Without accurate data concerning the amount of tips received from people dining in groups of different number of people, i.e. dining in groups of three, four, five, six, etc. respectively, we cannot evaluate if the general idea is not true.
(5)Granted that waiters and waitresses do receive less tips from large groups of people, we cannot hastily conclude that it is because people dining in a group are less likely to feel personally responsible for leaving an adequate tip.
注：题目中括号里的数字表明这句话体现的是提纲中第几号缺陷。
