GWD 17-30

tayleerchen

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?

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.
3. The written “Thank you” reminds restaurant patrons that tips constitute a significant part of the income of many food servers.
4. The rate at which people tip food servers in Pennsylvania does not vary with how expensive a restaurant is.
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.

答案B，我选E。不明白!

tengfeieric

大意：餐馆的服务生随机在一些账单上写上“谢谢”，看到“谢谢”的客人将多支付3%的小费。（结论）如果服务生有规律的写“谢谢”，则他们的小费收入将剧增。

B说，有规律的或经常性的看到“谢谢”不会改变顾客给小费的习惯。

如果有规律的看到“谢谢”会改变顾客给小费的习惯。那就无法得到题述的结论了。

bloomingtrees

选B.取非,即如果patrons 看到了谢谢后，会按照原来的方式给小费的话，那么总收入就不会比原来的多，平均收入也就不会都了．

Ｅ，取非．注意取非后这是不完全否定，即不是所有的人都会给得更多，这不能否定结论，因为还有一部分人会给得更多，那么平均数就多了．

tayleerchen

明白了!谢谢!

bloomingdales

我仍然不明白，如果这么说的话，那么改变他们原来的习惯，有可能是给得多，也有

可能是给的少了啊！请给我一个更加信服的反对E的理由~！

paopaodong

我刚才也跟楼上一样想的。现在想想B的道理在于，laihong用取非来做的。
题目问的是基于什么前提假设。
如果B不成立那么，结论肯定不成立。
如果E不成立，结论仍然可以成立。
所以b才是结论依赖的假设。