Tackling Find the Assumption Critical Reasoning Problems

Stacey Koprince —  October 22, 2012 — 15 Comments

gmat thank you
Find the Assumption questions are very common Critical Reasoning question types. If you don’t yet know the general process for tackling Critical Reasoning problems, learn how before you keep reading this article.

Ready to try a question? Set your timer for 2 minutes and try this GMATPrep problem:

In a study conducted in Canada, 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 Canada 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 Canada does not vary with how expensive a restaurant is.

(E) Virtually all patrons of the Canadian restaurants in the study who were given a bill with Thank you written on it left a larger tip than they otherwise would have.

Got your answer? Let’s start going through this one!

Step 1: Identify the Question

The question stem contains the word assumption, which is a pretty good clue that this is a Find the Assumption (FA) question. This question type always contains a conclusion and I know it’s important to find that conclusion. Also, if I can, I’m going to brainstorm any assumptions I can think of without taking too much time.

Step 2: Deconstruct the Argument

Here, I’ll show you what I’m thinking while I read the argument and also how I would take notes. Your own thought process won’t be exactly the same as mine and, of course, your notes will probably look quite different, since we all have our own ways of abbreviating things.

The Argument

What I Write

What I’m Thinking

In a study conducted in Canada, servers in various restaurants wrote Thank you on randomly selected bills before presenting the bills to their customers. FA     A  B  C  D  ECan: random TY bill Fact. They’re just setting up the scenario.
Tips on these bills were an average of three percentage points higher than tips on bills without the message. FA     A  B  C  D  ECan: random TY bill

Result: tips 3% ↑­ [why?]

 

They’re telling me the result “ tips were 3% higher “ but there’s absolutely no information about WHY. I can already tell what’s going to happen: the author’s going to make some big assumption about that.
Therefore, if servers in Canada regularly wrote Thank you on restaurant bills, their average income from tips would be significantly higher than it otherwise would have been. FA     A  B  C  D  ECan: random TY bill

Result: tips 3% ↑­ avg [why?]

© all TY = ↑↑­­ avg tips

 

And here we go. I can see multiple places to pick this apart. Significantly? Is 3% really significant? Also, will this always work? Maybe customers will get used to it and start ignoring it.

 

I’ve thought of a couple of different lines of attack. First, maybe there’s something around the word significant. Also, the author is assuming that what happened during the study will continue to happen in future, but maybe there’s some reason why that wouldn’t happen. I can imagine that I might respond by giving a larger tip the first couple of times I saw Thank you, thinking the server had taken extra care to write the note but if everybody did it, it wouldn’t have the same impact.

Note: I’m not really articulating all of the above to myself in so many words “ there’s not enough time. But quick ideas or impressions come to us as we read these arguments, and the above would be my general impression for this one.

Step 3: State the Goal

This is an assumption question, so I have to find something the author MUST believe to be true in order to draw this conclusion (that writing Thank you on the bill will result in significantly greater tips on average).

Work from Wrong to Right

 

Answer Choice

What I Write

What I’m Thinking

(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. FA     A  B  C  D  ECan: random TY bill

Result: tips 3% ↑­ avg [why?]

© all TY = ↑↑­­ avg tips

 

Regular vs. occasional? I don’t remember the argument making that distinction I glanced back at the argument and, nope, they don’t say anything about the type of customer. Wrong. (This one is what we call the irrelevant distinction trap. They’re trying to get us to think that a certain distinction might matter, but the argument doesn’t even talk about different types of customers.)
(B) Regularly seeing Thank you written on their bills would not lead restaurant patrons to revert to their earlier tipping habits. FA     A  B  C  D  ECan: random TY bill

Result: tips 3% â†‘­ avg [why?]

© all TY = â†‘↑­­ avg tips

new Cos

Would NOT lead this sentence is a little confusing. Let’s see. If I saw Thank you all the time, then I would NOT go back to giving lower tips. Hey, this is kind of what I said earlier: maybe if people see it all the time, they’ll stop giving good tips. So, yes, this does seem like something the author would have to assume to be true. I’ll leave this one in.
(C) The written Thank you reminds restaurant patrons that tips constitute a significant part of the income of many food servers. FA     A  B  C  D  ECan: random TY bill

Result: tips 3% â†‘­ avg [why?]

© all TY = â†‘↑­­ avg tips

 

That’s interesting. This answer gives a possible reason why someone might tip more when seeing Thank you. But it’s only a possible reason; the author doesn’t have to believe that this particular reason is definitely true in order to draw the conclusion. This answer would be fine if this were a strengthen question, but it’s not “ it’s an assumption question. Wrong.
(D) The rate at which people tip food servers in Canada does not vary with how expensive a restaurant is. FA     A  B  C  D  ECan: random TY bill

Result: tips 3% â†‘­ avg [why?]

© all TY = â†‘↑­­ avg tips

 

Hmm, maybe there are differences in how people tip depending on the level of the restaurant. How would this affect the conclusion? Oh, wait. It wouldn’t affect the conclusion at all. The conclusion doesn’t make any claim about the type or level of restaurant. This is another one of those irrelevant distinction trap answers, just like answer A!
(E) Virtually all patrons of the Canadian restaurants in the study who were given a bill with Thank you written on it left a larger tip than they otherwise would have. FA     A  B  C  D  ECan: random TY bill

Result: tips 3% â†‘­ avg [why?]

© all TY = â†‘↑­­ avg tips

 

Let’s see. In the study, the people who did get the Thank you bills gave larger tips than they otherwise would have. Yeah, you would have to assume that the servers didn’t randomly happen to choose people who were going to give those larger tips anyway. In other words, you do have to assume that the Thank you note did change people’s behavior. I’ll leave this one in, too.

 

We still have two answers left, B and E, so now we compare them.

Wow, I was pretty convinced when I read answer B, but now that I’ve read E, I think that one is it! Argh.

Okay, answer B addresses the issue of whether there would be an unintended consequence of seeing Thank you all the time “ if people who see it all the time then start ignoring it and go back to their old tipping habits, then the servers aren’t going to maintain that increase in their tips. Does the argument say that the result (significantly more in tips) would be short-term? No, it implies that this increase would be permanent. It wouldn’t be, though, if people did revert to their old tipping habits, so the author really does have to assume that people won’t go back to their old habits. B is still looking good.

What about E? I still like the fact that this answer says that the Thank you people gave larger tips than they otherwise would have. But both answers can’t be right! Is there anything else here? Oh, I think I see. At the beginning, the answer says that virtually all patrons gave higher tips. Is it necessary to assume that they all or almost all gave higher tips? Maybe a smaller portion gave much higher tips, and so the overall increase averaged to 3%. Let me just check the conclusion yes, I’ve got it! The conclusion also just talks about an average increase, so the author is not assuming that everyone gives higher tips “ just that some people do.

The correct answer is B.

Also, I’m pretty impressed by that wrong answer E. One part of it is an actual assumption “ the author does have to assume that the Thank you note did specifically cause the change in behavior. The problem with E was that it went too far in assuming that virtually all of the people changed their behavior. That was seriously tricky.

 

Take-aways for Find the Assumption (FA) CR questions:

(1) Know how to identify the question type. Most FA questions contain some form of the word assume or assumption, though occasionally the question will ask what information is required or what information would allow the conclusion to be more properly drawn.

(2) Deconstruct the argument according to the goals for this type. FA questions all have conclusions and they all hinge on finding some assumption, so I should be looking for these things as I read the argument. I don’t have endless time to brainstorm assumptions; I’ll have a better shot at thinking of one or two efficiently if I know to think about it while I’m reading the argument for the first time.

(3) Remind yourself of your goal. At first, you may need to say to yourself: For FA questions, I need to find something that the author must believe to be true in order to draw that conclusion. Some trap answers might involve something the author could believe to be true, but that’s not good enough. Longer term, you may be able to say to yourself, simply, “Find Assumption” and know what that entails.

(4) Cross off wrong answers first, then worry about finding the right answer. Don’t waste time trying to decide whether B is actually correct when you haven’t looked at C, D, or E yet. Eliminate first, then compare any remaining answers, as we did on this problem. Watch out for traps! On Assumption questions, one common trap answer tells us something that’s reasonable to believe could be true (such as answer C), but the author doesn’t absolutely have to believe that it’s true in order to get to his conclusion. Another common trap is the irrelevant distinction trap, where the answer tries to make a distinction between two or more groups or categories, but those distinctions do not actually matter to the given conclusion, as in answers A and D.

 

* GMATPrep questions courtesy of the Graduate Management Admissions Council. Usage of this question does not imply endorsement by GMAC.

 

Stacey Koprince

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Stacey Koprince is an Instructor and Trainer as well as the Director of Online Community for Manhattan Prep. She also co-manages the company's GMAT curriculum and product line. She has been teaching various standardized tests for more than fifteen years and her entire teaching philosophy can be summed up in five words: teaching students how to think.

15 responses to Tackling Find the Assumption Critical Reasoning Problems

  1. Thanks Stacey for such a nice explanation. I really like your short hands. I am learning it late though.

  2. Thanks Stacey for such a nice explanation. I really like your short hand notes. I am learning it late though.

  3. Thnaks this is a great explanation.. I hope I can apply it on this kind of questions..

  4. nice explanation.

  5. I luvd the way you explained it.

  6. Stacy –

    I maybe going overboard with this one but i should still ask this question for my own sanity. B states that the patrons will not revert back to their earlier tipping habits. Now, do we assume that their earlier tipping habits were bad and hence they will improve. Why cannot we assume that the patrons might not like ‘Thank you’ and that will cause them not to tip well. So not reverting to good tips will reduce the tip. (I understand that the scope of assuming things should not go beyond whats stated in the paragraph but assuming that the patrons have been giving good tips is also not stated)

    Choice A on the other hand has a definite increase.

    • We know that the earlier tipping habits were lower – because the point of the argument is that the Thank You notes caused the average tipping level to increase.

      Also note that we’re looking for what the AUTHOR assumes to be true. You can assume anything you want :) but the author cannot be assuming that the patrons won’t like the Thank You note and won’t tip well as a result because that would directly contradict his conclusion.

      One more thing: you say “assuming that the patrons have been giving good tips is also not stated.” By definition, assumptions are NEVER stated – assumptions are things the author of the argument must believe to be true in order to draw his/her conclusion, but the author does not actually state these things.

      If you have our CR book, I recommend reading the first chapter on the Assumption Family questions – it explains all about assumptions.

  7. ???? ?????, ???? ????????????? ???????!

  8. I was a little bit confused. But I read this article. Bang, it is quite simple logic ( really don’t need all these long assumptions). More TkU regularly, more tips? No! Once people get used to it, they will do the old ways. You need to exclude this— people won’t revert to old habits!

  9. Stacey,

    Thanks for the excellent explanation. After POE I was also left with B and E and chose E in 1:52 mins. After reading your explanation about “Average increase” in the question and “Virtually all”, I see why E is wrong. Now, I have gone thru the CR book in detail and answered all the Problem Set questions at the end of each chapter and find that I am consistently getting 75% of questions correct. What I fear is whether getting only 75% is good enough? I could of course get a higher percentage of answers correct but that would mean going over the 2 min limit which I am obviously avoiding. Is there something you could suggest that would help me in getting more answers correct within 2 mins for each question.
    I have read an article that you wrote some time back giving the analogy of tennis (not getting all answers right and still getting a good score overall) but what if the kind of questions I get are from the 25% that I get wrong. And last thing, there is no set pattern here regarding the ones I get wrong that I could isolate and focus on. I hope you can provide some guidance.

  10. Stacey,

    Thanks for the excellent explanation. After POE I was also left with B and E and chose E in 1:52 mins. After reading your explanation about “Average increase” in the question and “Virtually all”, I see why E is wrong. Now, I have gone thru the CR book in detail and answered all the Problem Set questions at the end of each chapter and find that I am consistently getting 75% of questions correct. What I fear is whether getting only 75% is good enough? I could of course get a higher percentage of answers correct but that would mean going over the 2 min limit which I am obviously avoiding. Is there something you could suggest that would help me in getting more answers correct within 2 mins for each question.
    I have read an article that you wrote some time back giving the analogy of tennis (not getting all answers right and still getting a good score overall) but what if the kind of questions I get in the real GMATe exam are from the 25% that I get wrong. And last thing, there is no set pattern here regarding the ones I get wrong that I could isolate and focus on. I hope you can provide some guidance.

  11. Hi.

    I’ve got the 4th and 5th edition of the CR strategy guide. However, Im a little bit confused regarding the way you explain Find the Assumption question. In the 4th edition you mentioned that there are 4 categories of assumptions but within the 5th edition thoses categories are not mentionned anymore. The only common thing Ive found is when you talked about the Negation technique.. Would you please let me know whether the 4 categories mentioned in the 4th edition is still applicable on today’s real gmat exam?? and where exactly would you set the 4 categories of assumptions (mentionned in the 4th edition) within the 5th edition??

  12. Utterly understand what your stance in this matter. Though Id disagree on some of the finer details, I feel you probably did an awesome job explaining it. Sure beats having to analysis it on my own. Thanks. Anyway, in my language, there arent a lot good supply like this.

  13. Hey just wanted to let you know that your content is very impressive, also Youre writing is wicked!, thanks again

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