Assumption questions ask you for a piece of support that isn’t explicitly stated but is necessary for the argument to remain valid. When a question asks you for what’s missing from the argument or what the argument depends on, then it’s asking you to find the author’s necessary assumption.
By first analyzing the question stem, you’ll know what to look for in the stimulus. For Assumption questions—and all questions based on arguments—untangling the stimulus consists of identifying the three parts of a GMAT argument: conclusion, evidence, and assumption.
The conclusion is the main point of the author’s argument. It’s the thing that the author is seeking to convince you of. There are three ways to identify the conclusions of arguments:
Evidence is provided to support the conclusion. GMAT arguments usually have little filler, so what isn’t the conclusion is typically evidence. Evidence can take the form of data, such as statistics, surveys, polls, or historical facts. Sometimes, however, the evidence is merely a conjecture or an opinion. The best way to identify an argument’s evidence is by examining its function within the argument: any material in the stimulus that provides support for the author’s conclusion is evidence.
All GMAT arguments contain one or more assumptions; identifying the assumptions is an essential step when answering any Critical Reasoning question based on an argument. An assumption is the unstated evidence necessary to make the argument work. It bridges the gap between two pieces of the argument, usually between conclusion and evidence but occasionally between two unconnected pieces of evidence. Without the assumption, the argument falls apart. You can think of it as something the author must believe but doesn’t directly state.
You can visualize the relationship between the various parts of an argument as follows:
Evidence + Assumption(s) → Conclusion
As you saw in the question about SlimDown diet supplement earlier in this chapter, you can usually predict an answer to an Assumption question. Your prediction is simply the argument’s assumption, which you already identified when you untangled the stimulus during step 2 of the Kaplan Method.
Let’s practice the whole process of untangling the stimulus and predicting the answer using this simple stimulus:
Allyson plays volleyball for Central High School. Therefore, Allyson must be over 6 feet tall.
The conclusion is the second sentence (signaled by the key word “[t]herefore”), and the evidence is the first. Is there a gap, or assumption, in this argument? Well, who’s to say that all high school volleyball players have to be over 6 feet tall? So you can confidently predict that the answer to an Assumption question would say something like this:
All volleyball players at Central High School are over 6 feet tall.
But what if the assumption doesn’t just jump out at you? How can you track it down? One of the most common ways the GMAT uses assumptions is to cover over mismatched concepts between evidence and conclusion. Notice that the argument above starts by talking about playing volleyball and then all of a sudden is talking about being over 6 feet tall. When tackling an Assumption question, look closely at the terms in each part of the argument. Is the scope of the evidence different, even if just slightly, from that of the conclusion?
Consider this seemingly solid argument:
Candidate A won the presidential election, carrying 40 out of 50 states. Clearly, Candidate A has a strong mandate to push for her legislative agenda.
At first glance, this sounds pretty good. But take a close look at the terms of the argument. The evidence is a win representing a sizable majority of states. The conclusion is about a strong mandate for an agenda. Even if you don’t notice the subtle difference between these two things, you could still make a prediction like this: Candidate A’s big victory means she has a mandate for her agenda. You’d be much more likely to recognize the right answer between these two possibilities:
The first answer choice doesn’t deal with Candidate A’s agenda at all. The second one shows a connection between her victory and her agenda, so it must be the right answer.
But what if you still aren’t sure that your answer choice is correct? Or what if the assumption is so subtle that you can’t predict the answer? In those cases, you can use the Denial Test.
An assumption must be true in order for the conclusion to follow logically from the evidence. Therefore, in an Assumption question, you can test each answer choice by negating it—in other words, imagining that the information given in the answer choice is false. If this negation makes the author’s argument fall apart, then the answer choice is a necessary assumption. If the argument is unaffected, then the choice is wrong. Let’s look at what you predicted earlier as the assumption in the volleyball argument:
All volleyball players at Central High School are over 6 feet tall.
Now let’s negate it:
Some volleyball players at Central High School are not over 6 feet tall.
Would Allyson still have to be over 6 feet tall? Not anymore. That’s why that prediction would be a necessary assumption. Keep in mind not to be too extreme when negating answer choices. The denial of hot isn’t cold but rather not hot. Similarly, the denial of all are isn’t none are but rather some aren’t.
Now let’s take another look at the answer choices for the question about Candidate A:
And now we’ll negate them:
Could Candidate A still enjoy a strong mandate? Definitely. Just because others in the past were as popular doesn’t mean that she doesn’t enjoy support for her agenda as well.
Now can Candidate A claim a mandate for her agenda? No, she can’t. That’s why the second choice is the correct answer for this Assumption question.
Give the Denial Test a try on your own using the following argument. Negate each answer choice and then ask, “Can the evidence still lead to the conclusion?”
I live in the city of Corpus Christi, so I also live in Texas.
The argument assumes which of the following?
The argument here is short and sweet, but it has all the essential elements of any GMAT argument. The conclusion is signaled by the key word so: the author lives in Texas. The author’s evidence is the claim in the first part of the sentence: he lives in Corpus Christi.
Rather than predict the correct answer right away, let’s test the answer choice statements using the Denial Test.
Negation of statement (A): Corpus Christi is not the only city in Texas.
Does that threaten the argument? No. There could be other cities in Texas, and it could still be valid to say that living in Corpus Christi proves that the author lives in Texas. The evidence could still lead to the conclusion, so choice (A) is not the assumption.
Negation of statement (B): There is at least one other city named Corpus Christi that is not located in Texas.
If this is true, does the conclusion still follow logically from the evidence? No. In this case, if there is another town named Corpus Christi located in, say, California or Florida, it would no longer be logically valid to say that the author must live in Texas because he lives in Corpus Christi. Choice (B) is a necessary assumption for the argument.
Negation of statement (C): If you have not been to Corpus Christi, you still could have been to Texas.
Note that when you are denying an if/then statement, you should deny the “then,” or result, portion of the statement. What impact does this negation have on the argument? None. Someone else could visit other cities in Texas, and still it may or may not be valid for the author to say, “I live in Texas because I live in Corpus Christi.” Choice (C) is not the necessary assumption.
Answers follow this exercise.
Now it’s time to put all these skills together and practice breaking down some arguments. First find the conclusion, then identify the evidence that supports that conclusion, and finally determine the central assumption(s). Once you’ve identified the assumption, try the Denial Test to confirm that the assumption you’ve identified is necessary for the argument to hold:
There are many ways to write a Critical Reasoning question. Any wording that suggests that you need to find a missing but vital piece of information indicates an Assumption question. Assumption questions are worded in some of the following ways:
Now let’s use the Kaplan Method for Critical Reasoning to solve an Assumption question:
When unemployment rates are high, people with full-time jobs tend to take fewer and shorter vacations. When unemployment rates are low, people tend to vacation more often and go away for longer periods of time. Thus, it can be concluded that full-time workers’ perceptions of their own job security influence the frequency and duration of their vacations.
The argument above assumes that
The word “assumes” in the question stem is a clear indication of an Assumption question.
“Thus” signals the argument’s conclusion. You could paraphrase it as follows: how much vacation time full-time workers take depends on how secure they feel in their jobs. The author’s evidence for this conclusion is the relationship between vacations and unemployment. When unemployment is high, workers take fewer and shorter vacations; when unemployment is low, the opposite happens.
To find the central assumption, use Critical Thinking to link the terms in the evidence with the terms in the conclusion. Since the evidence centers on employment levels and vacations, while the conclusion centers on job security and vacations, the central assumption must center on the connection between employment levels and job security.
Choice (D) matches this prediction, bridging the terms of the evidence with the terms of the conclusion. The Denial Test can help confirm (D) as the correct answer; if there were no relationship between workers’ perceptions of job security and the unemployment rate, then it would no longer make sense for the author to use evidence about the unemployment rate to support a conclusion about workers’ perceptions of job security. (D) is an assumption necessary for the argument to hold.
The other choices are all incorrect in some definable way. It’s great practice to identify exactly why each wrong choice is wrong. Doing so will help you develop your Pattern Recognition skills so you can identify common wrong answer types on Test Day. (A) is too extreme (“no fear of losing their jobs”) to be the necessary assumption. (B) introduces the idea of travel costs, which have no necessary connection to job security in the conclusion. (C) is incorrect because whether those people who work full-time jobs prefer to work them is irrelevant. (E) tells us that workers’ perceptions of their job security have deteriorated lately, but that has no necessary connection to the unemployment rate. Remember that the assumption must successfully link the evidence to the conclusion.