[求助]GWD17-30

Q30:

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?

选B！

assumption题目，首先找否定词not，然后去掉not，看能不能weaken，如果weaken就是答案。这是狒狒逻辑宝典中的重要定理。

所以B选项去掉not，就是说，客人如果经常看到thank you的标记，就会回到以前的付小费的方式，那么自然不会多给那个3％，削弱结论。

A选项取非，就是说，thank you标记对于常客和临时的客人，影响不一样，那么到底多付小费还是少付小费，不知道。

right。应该是B。

狒狒关于assumption的定理应用范围广么？

Q30:

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.

推导关系为，发现偶尔地写谢谢在帐单上会刺激顾客多给小费-----每张都写，那小费会显著增加。

Which of the following is an assumption on which the argument relies?

1. 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.


2. Regularly seeing “Thank you” written on their bills would not lead restaurant patrons to revert to their earlier tipping habits.  取非， 经常看到谢谢，人们将会到以前给小费的习惯，即不详一开始看到谢谢时那样多给小费了


3. The written “Thank you” reminds restaurant patrons that tips constitute a significant part of the income of many food servers.无关


4. The rate at which people tip food servers in Pennsylvania does not vary with how expensive a restaurant is. 无关，只是消费有没有增量， 而无关增加多少


5. 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. 增强原推导关系的依据， 而且这个选项中有绝对词all，试想， 一个人赖以推导的假设不太可能是很绝对的说法，发现绝对词排除法在逻辑和阅读中都有限有效。

B是没有疑问的,所谓物以稀为贵,要是每个都写THANK YOU,看多了,谁还会为这个给多的小费啊

这个推理的基础就是,人们给小费的习惯不会因为每次都看到这样的THANK　ＹＯＵ而改变