How to infer on the GMAT (RC)

How to infer on the GMAT (RC)

-From the Mnahattan GMAT Blog

We’re going to kill two birds with one stone in this week’s article.

Inference questions pop up on both Critical Reasoning (CR) and Reading Comprehension (RC), so you definitely want to master these. Good news: the kind of thinking the test-writers want is the same for both question types. Learn how to do Inference questions on one type and you’ll know what you need to do for the other!

That’s actually only one bird. Here’s the second: both CR and RC can give you science-based text, and that science-y text can get pretty confusing. How can you avoid getting sucked into the technical detail, yet still be able to answer the question asked? Read on.

Try this GMATPrep® CR problem out (it’s from the free practice tests) and then we’ll talk about it. Give yourself about 2 minutes (though it’s okay to stretch to 2.5 minutes on a CR as long as you are making progress.)

“Increases in the level of high-density lipoprotein (HDL) in the human bloodstream lower bloodstream cholesterol levels by increasing the body’s capacity to rid itself of excess cholesterol. Levels of HDL in the bloodstream of some individuals are significantly increased by a program of regular exercise and weight reduction.

“Which of the following can be correctly inferred from the statements above?

“(A) Individuals who are underweight do not run any risk of developing high levels of cholesterol in the bloodstream.

“(B) Individuals who do not exercise regularly have a high risk of developing high levels of cholesterol in the bloodstream late in life.

“(C) Exercise and weight reduction are the most effective methods of lowering bloodstream cholesterol levels in humans.

“(D) A program of regular exercise and weight reduction lowers cholesterol levels in the bloodstream of some individuals.

“(E) Only regular exercise is necessary to decrease cholesterol levels in the bloodstream of individuals of average weight.”

Got an answer? (If not, pick one anyway. Pretend it’s the real test and just make a guess.) Before we dive into the solution, let’s talk a little bit about what Inference questions are asking us to do.

Inference questions are sometimes also called Draw a Conclusion questions. I don’t like that title, though, because it can be misleading. Think about a typical CR argument: they usually include a conclusion that is…well…not a solid conclusion. There are holes in the argument, and then they ask you to Strengthen it or Weaken it or something like that.

When the test writers asks you to infer something, they are not asking you to draw that kind of conclusion. They’re not even asking you to infer in the way that we normally use that word in the real world. Rather, they are asking you to deduce something that must be true according to the available information in the argument or passage.

Cats are my favorite type of pet. What can you infer from that statement?

In the real world, you might think that I have a cat, or that I’ll play with or pet your cat if I come over to your place, or that if you asked me to choose between a free pet cat and a free pet lizard, I would obviously choose the cat.

There’s just one little problem. I’m seriously allergic to cats. So, while those scenarios might be generally likely for someone who says that cats are her favorite type of pet, not one of the scenarios has to be true.

What does have to be true? I don’t like dogs as pets better than I like cats as pets. (To all my dog-lover readers: I do like dogs. They just require more care. And anyway, I’m allergic to both, so the point is moot for me. J)

It also must be true that I am familiar with at least one other type of pet; otherwise, I couldn’t make the judgment call to say that cats are my favorite type of pet.

This, then, is what we need to find among the answer choices: something that must, unequivocally, be true according to the evidence they gave us in the argument or passage.

Okay, ready to talk about the problem?

Step 1: Identify the Question

What kind of question type is it? The word inferred is the giveaway: this is an Inference question type. They may also use language like (emphasis added):

Which of the following assertions is most strongly supported by the evidence above?

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

Once you know the question type, you also know that the argument will contain only premises, no conclusion, and your task will be to deduce something that must be true from that information.

Step 2: Deconstruct the Argument

Okay, now let’s tackle the crazy technical language of the argument.

Here’s what I thought and wrote while I did the problem. 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. (Note: Inf = inference.)





Okay, I need to compare (B) and (D).

“(B) Individuals who do not exercise regularly have a high risk of developing high levels of cholesterol in the bloodstream late in life.”

“(D) A program of regular exercise and weight reduction lowers cholesterol levels in the bloodstream of some individuals.”

They both match a lot of the language in the passage, but when I re-read carefully, I noticed an extra detail in answer (B): “late in life.”

The argument doesn’t say anything about when this stuff happens: when we’re young, middle-aged, old. I could imagine that people have higher risk later in life…but that’s the same as you imagining that I would play with your cat, since I like cats so much. It might be true, but it doesn’t have to be true.

Answer (D), on the other hand, doesn’t go beyond the scope of the argument at all. In fact, it matches the final chain we put together for the argument: I go to the gym and lose weight, that raises my HDL, and that lowers my cholesterol. Yay! Note also that this answer choice is very middle-of-the-road: it claims that this will work only for “some individuals,” which is exactly what the argument says.

The correct answer is (D).

Take-aways for Inference and science-y questions:

(1) Your goal on an inference question is to deduce something that must be true given the evidence in the argument or passage. Don’t go beyond what the text says and don’t make a “real-world” inference (something that could be true but doesn’t have to be true).

(2) Ignore the science! Well, no, you can’t ignore it entirely. But you can ignore some of it. Start by using your SC skills to look at just the basic sentence: the subject and the verb. Then start adding in the extra info, piece by piece.

(3) Did you notice that we never had to go back to that last part of the first sentence, exactly how the body’s cholesterol levels are lowered? Sometimes, you can ignore some of the technical info forever. If possible, just try to understand why it’s there, not necessarily what it’s actually saying, so that you’ll know later whether you need to come back to it. (In this case, I knew that it was trying to explain why cholesterol levels went down. But I never needed that info!)