这道题的样本是什么？为什么说B选项提到了样本，而E选项没有？根据统计枚举推理方法来做这个题，很难把握什么是真正的样本，有没有大神指点一下如何找样本啊？逻辑笔记里没有讲这个最关键的方法
另外我觉得这个题的样本是“在此次研究中的随机写有thank you的这些bill”，而B选项不符合这个要求，所以无法解释选择B选项的理由！
In a study conducted in Pennsylvania, servers in various restaurants wrote “Thank you” on randomly selected bills before presenting the bills to their customers. Tips on these bills were an average of three percentage points higher than tips on bills without the message. Therefore, if servers in Pennsylvania regularly wrote “Thank you” on restaurant bills, their average income from tips would be significantly higher than it otherwise would have been. Which of the following is an assumption on which the argument relies? A. The “Thank you” messages would have the same impact on regular patrons of a restaurant as they would on occasional patrons of the same restaurant. B. Regularly seeing “Thank you” written on their bills would not lead restaurant patrons to revert to their earlier tipping habits. C. The written “Thank you” reminds restaurant patrons that tips constitute a significant part of the income of many food servers. D. The rate at which people tip food servers in Pennsylvania does not vary with how expensive a restaurant is. E. Virtually all patrons of the Pennsylvania restaurants in the study who were given a bill with “Thank you” written on it left a larger tip than they otherwise would have. | 
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发表于 2013-10-27 19:30:34
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