Critical Reasoning
Verbal
10 min readStrengthening arguments is one of the most common Critical Reasoning tasks on the GMAT Focus Edition. In these questions, you are given a short argument, and your job is to pick the answer choice that makes the argument's conclusion more likely to be true. This study guide will teach you the foundational skills you need to handle these questions with confidence, even if you are just starting your GMAT preparation.
Every Critical Reasoning passage on the GMAT contains an argument. An argument is a set of statements where some statements (the premises) are offered as reasons to believe another statement (the conclusion). For example:
A strengthening question asks you to choose an answer that makes the conclusion more likely to be true. You are not asked to prove the conclusion absolutely. You are only asked to add a piece of information that supports the argument in some way.
The GMAT tests this skill because it mirrors real-world decision-making. In business, you often have to evaluate whether a proposed course of action is wise, or whether a claim is well supported. Being able to identify what additional evidence would make a conclusion more credible is a valuable analytical skill.
To strengthen an argument, you first need to understand its structure. Every argument has at least one premise and one conclusion. Often there is also an assumption, which is an unstated premise that the argument relies on.
Consider this argument:
This argument assumes that the tax credit was the reason for the sales increase. But there could be other explanations: maybe gas prices rose, or maybe new models were introduced. To strengthen this argument, you could provide evidence that rules out an alternative explanation, such as: “During the same period, gas prices remained stable.” That makes it more likely that the tax credit was indeed the cause.
Another way to strengthen is to support a premise directly. If a premise is weak or questionable, adding evidence that makes it more believable strengthens the argument. For example, if the premise was “Sales increased,” you could strengthen it with “Sales data from all major dealerships confirm the increase.”
Strengthening questions are usually easy to identify because of their question stems. Look for phrases like:
Sometimes the stem may say “most strengthens” or “best supports.” The word “if true” is important: you must accept every answer choice as true, regardless of whether it is actually true in the real world. Your job is to see which one, if true, would help the argument.
Follow these steps for every strengthening question:
Wrong answers in strengthening questions tend to follow a few common patterns. Recognizing these patterns will help you eliminate them quickly.
An answer that talks about something unrelated to the argument is out of scope. For example, if the argument is about the effect of a new training program on employee productivity, an answer about employee satisfaction is probably out of scope, unless satisfaction is directly linked to productivity in the argument.
Some answer choices actually make the conclusion less likely. These are the opposite of what you want. For example, if the conclusion is that a new drug is effective, an answer that says the drug has serious side effects might weaken the argument (though side effects are not always relevant to effectiveness). Always check whether the answer helps or hurts.
An answer that compares the argument to an unrelated situation is not helpful. For instance, if the argument is about Company A's sales, an answer about Company B's sales is irrelevant unless there is a clear connection.
Answers that use words like “all,” “never,” “always,” or “none” are often too strong and may be wrong, especially if the argument is about a tendency or a likelihood. However, extreme language is not automatically wrong; it depends on the argument.
Supporting a premise can strengthen the argument, but the answer must ultimately make the conclusion more likely. An answer that only gives more detail about a premise without connecting to the conclusion may not be enough.
Argument: A recent survey of 1,000 adults found that 80% prefer coffee over tea. Therefore, coffee is more popular than tea among all adults.
Question: Which of the following, if true, most strengthens the argument?
Answer choices:
Solution: The conclusion is that coffee is more popular than tea among all adults. The premise is a survey of 1,000 adults. The gap is whether the sample is representative. Choice B directly addresses that: if participants were randomly selected from all adult groups, the sample is likely representative, making the conclusion more likely. Choice A does not help because online surveys may still be biased. Choice C is irrelevant. Choice D is irrelevant. Correct answer: B.
Argument: A city installed new traffic lights at a busy intersection. In the following month, the number of accidents at that intersection decreased by 30%. Therefore, the new traffic lights caused the reduction in accidents.
Question: Which of the following, if true, most strengthens the argument?
Answer choices:
Solution: The conclusion is that the new lights caused the accident reduction. The argument assumes that there is no other cause. Choice C rules out other changes, eliminating an alternative explanation, which strengthens the causal claim. Choices A and B introduce alternative explanations (more patrols, lower speed limit) that would weaken the argument. Choice D is irrelevant because it talks about other intersections. Correct answer: C.
Argument: A company plans to launch a new product. The company conducted a survey of 500 customers, and 90% said they would buy the product. Therefore, the product will be a commercial success.
Question: Which of the following, if true, most strengthens the argument?
Answer choices:
Solution: The conclusion is that the product will be a commercial success. The premise is that 90% of surveyed customers said they would buy it. The argument assumes that the surveyed customers are representative of the actual market. Choice B directly supports that assumption, making the conclusion more likely. Choice A helps with survey credibility, but it does not guarantee representativeness. Choice C and D are weak because they do not directly address the link between the survey and actual sales. Correct answer: B.
Even at the beginner level, there are a few nuances to keep in mind.
A strengthener does not have to prove the conclusion. It only has to make the conclusion more likely. For example, if the conclusion is that a new drug is effective, a strengthener could be that the drug was tested on a diverse group of patients. That does not prove effectiveness, but it makes the results more credible.
Some answer choices may be true and relevant, but they may strengthen the argument only slightly. The correct answer is the one that strengthens the most. This means you need to compare the relative impact of each answer. A direct, strong connection to the conclusion is usually better than an indirect, weak connection.
Sometimes an answer provides numerical data that strongly supports the conclusion. For example, if the conclusion is that a marketing campaign increased sales, an answer that says sales increased by 50% in the target region is strong. However, you must ensure the data is relevant to the conclusion.
With practice, you will develop an instinct for what makes an argument stronger. Remember: your job is not to be a skeptic, but to be a helpful friend who brings the best supporting evidence to the table.
Free Critical Reasoning questions on this topic — try a few now.