Evidence Family – Inference Questions

The inference question type forms part of the Critical Reasoning Evidence Family.

Evidence Family questions are made up entirely of premises, and contain no assumptions either. The family/group has two main types of questions: Inference and Paradox.

Before you proceed to learning how Inference questions can be answered correctly, you must first understand what an inference is. What does the GMAT mean when it asks us to infer something?

Strictly by GMAT standards, an inference is something that has to be true according to the evidence(s) presented in the argument. Now, what you must know is that this is very different from how “inferences” are perceived in the real world, where an inference is something we derive from available evidence (information) and is hence only likely to be true (not definitely true). Therefore, the kind of logical reasoning that you show when you make these GMAT-specific inferences are meant to be very different from the real-world ones, which pretty much amount to making an educated guess about something based on the information that has been provided about it already.

For e.g.

Fact: Saturday is the worst day of the week, and I’m often late to work.

Real-world inference(s): I am quite punctual to work on Weekdays.

GMAT inference: I like Sundays more than I like Saturdays.

Inference questions require us to find an answer that must be true according to the information provided in the argument (containing only one or more premises). More often than not, you will be required to use only some of the information presented in the argument, though you may of course use all of it.

Inference question stems usually contain some form of the words “conclude” and “infer”, though you’ll often find variations that don’t include those specific words.

Some examples of inference question stems:

1. Which of the following can be “logically concluded” from the given text?
2. The statements above most “strongly support which of the following conclusions”?
3. Which of the following can be “properly inferred” from the given statements?
4. The statements made “best support” which of the following “assertions”?
5. Which answer “must be true” based on the above statements?

While attempting “Inference” questions, it’s important to remember not to confuse them with “Strengthen the Argument” questions. When stems contain the language “most strongly support”, it’s easy to be misguided into thinking that the question may be asking you to look for answer choices that strengthen the argument.

The best way to remember the difference between the two is by noting that:

• On Inference questions, the argument (above) given should support the correct answer choice (below). [Use the argument given to support the answer]
• On Strengthen the Argument questions, the correct answer choice (below) will support the conclusion given in the argument (above). [Use an answer to support the argument]

Also remember that Inference questions will only have premise(s) in the argument text, whereas Strengthen questions will certainly have more than just the premise(s), and usually always a conclusion.

Let’s take a look at an example:

Both enrollment and total tuition revenue at Brownsville University have increased during each of the last four years. During the same period, enrollment at Canterbury University has steadily decreased, while total tuition revenue has remained constant.

Which of the following hypotheses is best supported by the statement given?

(A) Brownsville University now collects more total tuition revenue than does Canterbury University.

(B) The per-student tuition at Canterbury University has risen over the last four years.

(C) Brownsville University will continue to increase its revenues as long as it continues to increase enrollment.

Answer:

Let’s break the argument down to its core:

Premise(s): “Both enrollment and total tuition revenue at Brownsville University have increased during each of the last four years. During the same period, enrollment at Canterbury University has steadily decreased, while total tuition revenue has remained constant.”

We can understand the following as the core of the argument:

Note that, on all inference questions, the right-hand side of the core will always look like the above because you will only always be given premises.

Now, if we carefully consider all the given answer choices and match them up against what has been provided as the premise(s), we shall see the following:

Option A suggests that Brownsville University now collects more total tuition revenue does Canterbury University does. For this option to be correct, we need a surefire indication that the tuition at BU is in fact, numerically higher. However, in the given set of premises, only the change in trends at the two universities has been mentioned, and the actual comparison in terms of tuition fee has not been done. Thus, this inference cannot be made.

Option B suggests that the per-student tuition at Canterbury University has risen over the last four years. For this option to be correct, we need information on per-student enrollment because the fee comes in only during enrollment. And we know that enrollment has gone down! Now, if the tuition revenue has not gone down with the downward enrollment pattern, then per student must be paying more. So, yes this does seem like the correct answer!

Option C suggests that Brownsville University will continue to increase its revenues as long as it continues to increase enrollment. Now this option is certainly a plausible inference, if we are to consider it a real-world hypothesis. However, this information is not an absolute certainty as per the given premises. Hence, this option is incorrect.

Clearly, option B is the correct answer.