In a study conducted in Pennsylvania, servers in various restaurants

The argument is that if servers write "thank you" then on AVERAGE their income will be significantly HIGHER than it would have been otherwise.
This is based on a study that found that when servers did this their tips, on average, increased by 3%

What is assumed here?
A - neither the argument nor evidence distinguishes among patron types - eliminate.
B - if writing "TY" is the new norm and patrons revert back to old tipping proportions then this would decrease the average amount tipped. Thus, B denies the possibility that this happens and thus MUST BE TRUE in order for the argument to be true
C Incorrect as this doesn't need to be assumed in the increase/ decrease effect of writing thank you
D If the rate at which people tip food servers does vary with how expensive a place is then this doesn't really affect the argument at hand.

Louis vuitton store bill: $1000
Tip when writing thank you: $300
= 30% tip

Generic clothing store bill: $100
Tip when writing thank you: 30
= 30% tip

The tip amount is still higher when writing thank you, but the underlying base may be different. This is where D tries to trick you.

E attempts to fool you into thinking that solidifying the effect deduced from the study will need to be assumed to make the argument. This may not be true. We could merely have sighted evidence from say 60% of participants to deduce the effect.

Hi IanStewart

Could you please help with this question?

I could understand why (E) is wrong.




We don't neccessarily have to assume that Virtually all patrons in the study who were given a bill with “Thank you” written on it left a larger tip than they otherwise would have. The conclusion would still be ok even if 40% of those patrons left a larger tip than usual.

Yet, I couldn't completely comprehend why (B) is correct.

Could you please explain why (B) is correct?

Thank you very much beforehand!

Yes, E is wrong because the argument is only about averages. As long as tips are larger on average, the servers make more money, and it doesn't matter if every tip is 3% larger, or if one tip is huge and 99% of tips are unchanged.

Here we have a small-scale experiment which produced a 3% increase in tips. If we're going to translate that to a large-scale experiment (where servers always write 'thank you' on bills), then if we're expecting we'll still see a 3% increase in tips, we're assuming nothing will change as we scale things up. That is, we're assuming customers will behave the same way if they always see 'thank you' on their bill as they did in the small-scale experiment where they were seeing 'thank you' on their bill for the first time (or at least when they only rarely saw 'thank you' on a bill). So that's why B is right.

There are a lot of similar arguments, in the real world and on the GMAT, which make a similar assumption. For example, and this is not based on any actual facts about limes, I'm just inventing a scenario: if a two-week-long study proved that eating a lime every day improved people's moods, and based on that data, dieticians suggested everyone should eat limes every day to improve mood long-term, that conclusion would be assuming that people don't build up a tolerance for or immunity to the happiness-producing effects of limes. That is, the conclusion is assuming when you scale things from a short two-week study to a permanent behaviour, people continue to respond identically. That may or may not be true.

(E)? If we write "thank you" or not, they would have still left it?

Hi Laksya

No, that is not the reason for (E) being incorrect.

The question asks us identify the underlying assumption for the conclusion that, "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", based on the results of the experiment stated before this statement. Which means, to draw this conclusion from the given results, what assumption needs to be true.

Option (E) is not required to be true for this conclusion from these facts ie; given these results, the conclusion is neither strengthened nor weakened whether (E) be true or not. If you negate (E), the conclusion is not negated.

Hope this answers your question.

EducationAisle sir,

Please evaluate my reasoning.

Option A:- This is incorrect because the argument above does not talk anything about the impact of "Thank you" messages on regular and occasional patrons. The argument does not say that the impact leads to higher tipping. Hence, this is incorrect.

Option B:- This is the correct answer. When negated the conclusion breaks down. Regularly seeing "Thank you" would lead patrons to revert to their old habits. Hence, this would break the conclusion.

Option C:- No impact on our argument. The passage above does not draw a link between reminding and high tipping. Hence, this is incorrect.

Option D:- Incorrect. Varying tipping and restaurant expense does not have any impact on the high tipping. Plus when we negate this option statement we get " The rate varies with how expensive the restaurant is". So our conclusion still stands because we don't know whether that variation is towards the higher side or not. Hence, this cannot be assumed.

Option E:- This is an interesting one. I initially marked this one. This is irrelevant too because this restates the information already mentioned in the passage. How many people left a larger tip is not our concern. We concluded from the study that seeing a thank you leads to higher tipping. Out of all the people in the study all left a larger tip or 70 percent or 50 percent. It doesn't matter. The outcome is that we have concluded something from the study. Hence, this is the incorrect answer.

Please share your two cents on my reasoning above.

Thanks

Would agree also note that A is incorrect because the argument does not differentiate between regular patrons and occasional patrons. For example, regular patrons may give 2% extra tip, while occasional patrons may give 4% extra tip, but the argument still holds true.

the logic behind B is that
seeing the thank you more and more , makes this message ordinary . people will not react to it in future.
it means people become used to it . so , this message losses its effectivenss

Why is it not E, because we have not been prompted in the question that normally also those people would not have tipped a better amount?

Here's (E):

(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.

In a GMAT Assumption question, the correct answer must state something additional that's necessary for the argument to work.

In this case, the argument has already presented the following evidence:

Tips on these bills were an average of three percentage points higher than tips on bills without the message.

That evidence is sufficient to support the conclusion even if what (E) says isn't true. After all, if it's the case that, on average, people left a greater tip when the server wrote "Thank you" on the bill, then it's reasonable to conclude that "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."

After all, as long as the average tip is bigger, the servers' incomes will be higher, even if not all patrons leave bigger tips.

So, the argument doesn't depend on it being true that virtually all the patrons who were given bills with "Thank you" written on them left larger tips than they otherwise would have. It still works even if that isn't true.