Tackling a GMATPrep Critical Reasoning Inference Problem

Stacey Koprince —  March 22, 2012 — 6 Comments

lie detector

This week, we’re going to discuss one of the most common critical reasoning problem types: Inference. (Note: our current materials call these questions Draw A Conclusion, but we’re changing the name next month!) If you haven’t yet, read this article before we try our GMATPrep problem. Then set your timer for 2 minutes and go!

* When a polygraph test is judged inconclusive, this is no reflection on the examinee. Rather, such a judgment means that the test has failed to show whether the examinee was truthful or untruthful. Nevertheless, employers will sometimes refuse to hire a job applicant because of an inconclusive polygraph test result.

Which of the following conclusions can most properly be drawn from the information above?

(A) Most examinees with inconclusive polygraph test results are in fact untruthful.

(B) Polygraph tests should not be used by employers in the consideration of job applicants.

(C) An inconclusive polygraph test result is sometimes unfairly held against the examinee.

(D) A polygraph test indicating that an examinee is untruthful can sometimes be mistaken.

(E) Some employers have refused to consider the results of polygraph tests when evaluating job applicants.


Okay, now that you’ve got an answer, let’s use our 4-step CR process.

Step 1: Identify the Question

First, we read the question stem:

Which of the following conclusions can most properly be drawn from the information above?

The key identifying language is typical in this example. The language which of the following conclusions indicates that the answer choices contain conclusions, or inferences. This, coupled with the language can most properly be drawn, indicates that we have an Inference (or Draw a Conclusion) question.

The question language is generic in the sense that it doesn’t provide us with any details about the argument. We do know several things, though. First, the argument we’re about to read will not contain any conclusion itself “ it will consist only of premises, and those premises are usually fairly factual on this question type. Second, our task will be to find an answer that must be true given some or all of those premises.

Step 2: Deconstruct the Argument

I already know that all of the sentences will contain premises “ but what will be the flow of the information? Will the premises all be separate or will some pieces of information lead to others?

The first sentence indicates that (a) it’s possible for a polygraph test to be inconclusive and (b) when this happens, it doesn’t tell us anything about the examinee. Rather, the second sentence says, this just means that the test has failed to do what it was supposed to do. The test has failed, not the examinee. The third sentence begins nevertheless “ what does that word mean? It means Despite what I’ve told you so far, some contradictory thing comes next. Despite the fact that an inconclusive result only means that the test has failed, employers sometimes decide not to hire someone because of that inconclusive result.

That’s ridiculous! It’s not my fault that the test failed! (You don’t really need to go this far in your thinking while reading the argument, but sometimes putting ourselves into the situation can help. : ) )

Your notes might look something like this (though there are lots of ways to write notes!):

Inconcl PT = test fail; don’t know about employee
BUT employer st won’t hire b/c of that

Note that I used abbreviations; you can use any you want as long as they make sense to you. My typical abbreviation for sometimes or something is “st. Note that I didn’t label anything the conclusion “ because there isn’t one. Those are all just facts.

Step 3: State the Goal

Our goal is to find an answer that must be true given some or all of the information presented in the argument. Note that we do not need to use all of the information. There will be only one answer that must be true, given the information in the argument.

The most common trap on this type is something that could be true and might even be likely to be true but does not absolutely have to be true.

Step 4: Work from Wrong to Right

(A) Most examinees with inconclusive polygraph test results are in fact untruthful.

I have no idea if this is true. The argument didn’t address whether the people who receive inconclusive polygraph results are likely to be truthful or are not likely to be truthful. In fact, it specifically says that we can’t tell. Eliminate A.

(B) Polygraph tests should not be used by employers in the consideration of job applicants.

I can believe that there are some people who would believe this or advocate for this, but the author of the argument never comments on how the tests should or should not be used. This doesn’t have to be true.

(C) An inconclusive polygraph test result is sometimes unfairly held against the examinee.

Let’s see. If an examinee were to get an inconclusive result and then not be hired specifically for that reason, then that would be unfair, yes “ since the inconclusive result doesn’t actually mean that the person was being untruthful. Does this ever happen? Yes, the last sentence says that employers will sometimes do this “ just as the answer choice says that this sometimes happens.

In other words, it is possible to be truthful and get an inconclusive result, and it is possible to be untruthful and also get an inconclusive result. Sometimes, people will not be hired because they have an inconclusive result, so it’s possible to be truthful and yet not get hired. According to the argument, this answer choice is true; let’s keep it in and check the remaining answers.

(D) A polygraph test indicating that an examinee is untruthful can sometimes be mistaken.

I can believe that this is true in the real world but the argument never discusses a situation where a person gets an untruthful result from the test. The argument only discusses the case of the inconclusive result. So I can’t infer anything for sure about an untruthful result.

(E) Some employers have refused to consider the results of polygraph tests when evaluating job applicants.

Again, I can believe that this is true, but this circumstance doesn’t apply to the argument. The argument mentions employers who do use the polygraph results, not those who do not.

The correct answer is C.

Answers A, B, D, and E all represent speculations “ things that we might brainstorm about such a situation, but that may or may not be true. Maybe an inconclusive result happens most often when someone knows how to beat polygraph tests, and so the person lies but gets away with it. If that were true, then answer A might be true but we were given no actual evidence to support this idea.

Key Takeaways for Solving Inference CR Problems:

(1) Know how to recognize this type. The question stem will typically use some variation of the word conclusion or infer. It will also mention something along the lines of most properly drawn or best supported by. Be careful about one thing: Inference questions can sometimes include the words strongly supports and this language also shows up in Strengthen questions. If the question contains this language, check to see whether it refers to the answers as conclusions or inferences “ if so, this is an Inference question, not a Strengthen question. (Strengthen questions will contain a conclusion in the argument, not in the answer choices.)

(2) Know what to do with Inference questions. The argument will contain fact-based premises and no conclusion. Our goal is to find an answer that must be true given some or all of the premises. We don’t need to use all of the information in the argument.

(3) Watch out for traps! The answer choices usually contain Real World inferences: things that might be or are even likely to be true in the real world but they don’t absolutely have to be true. These are tricky because we’re used to making reasonable assumptions in the real world when drawing a conclusion or inference “ but we can’t do that on the GMAT.

* 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's also a management consultant who specializes in corporate strategy. 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.

6 responses to Tackling a GMATPrep Critical Reasoning Inference Problem

  1. Awesome article. Very recently I found out that CR and RC inference questions are one of my weaknesses and this article and the one that is linked within are awesome. I have studied both of them thoroughly and I strongly feel that now I have a better understanding of what is that I have to do on Inference based questions. Thanks a ton Stacey!!

    Ameya

  2. Hi Stacey,

    Thanks for the insights, I have been reading through the blog and especially your articles and found them to be very useful. I have mentioned you and Manhattan GMAT blog on my blog-post ( linked below). Keep posting.

    http://knowingthepathandwalkingthepath.blogspot.in/2012/04/gmat-strategy-series-cr-strategy.html

  3. great Stacey :)

    I guess the level of this one is at least 650. isn’t it ???

  4. very useful article indeed! Thank you stacey !

  5. Thanks Stacey for this article! Inference questions are my weakness area -you do a great job explaining. Thanks for sharing!

  6. KiyaBeautifulWORDS this is like a comment about Jebadiah

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