The GMAT tests your understanding of arguments with several question formats, including: Conclusion (Inference), Assumption, Weakening/ Strengthening, Evaluation, Flaw, Paradox, and Parallel Structure.
An inference is simply a type of conclusion. Although the GMAT often asks conclusion questions that require you to choose the answer that is a summary of the argument, the test makers may take you in unexpected directions and ask you to select a correct answer choice that is based on only some of the information provided. In either case, the validity of the argument is the important factor that leads you to only one answer choice.
Here is a conclusion question similar to those found on the GMAT:
Increases in funding for police patrols often lower the rate of crimes of opportunity such as petty theft and vandalism by providing visual deterrence in high-crime neighborhoods. Levels of funding for police patrols in some communities are increased when federal matching grants are made available.
Which of the following can be correctly inferred from the statements above?
- Areas with little vandalism can never benefit from visual deterrence.
- Communities that do not increase their police patrols are at higher risk for crimes of opportunity late at night.
- Visual deterrence is the most effective means of controlling petty theft.
- Federal matching grants for police patrols lower the rate of crimes of opportunity in some communities.
- Only federal matching grants are necessary to reduce crime in most neighborhoods.
The correct answer, D, is a summary of the information provided; it is the logical end of a chain of reasoning started in the stimulus argument. A logical map of the chain might look something like this:
Increased funding → Increased visual deterrence → Lower crime
The last statement could be mapped as follows:
Federal grants → Increased patrol funds
Answer choice D makes the chain complete by correctly stating that federal grants can lead to lower crime in some communities. Now the logical chain appears thus:
Federal grants → Increased funding → Increased visual deterrence → Lower crime
The other answer choices may not be correctly inferred because they go beyond the scope of the argument. They may be objectively, factually correct, or they may be statements that you would tend to agree with. However, you are limited to the argument presented when choosing a correct answer.
Following are some other question stems that the GMAT uses to indicate conclusion/inference questions:
- If the above statements are true, which of the following must be true?
- Which of the following conclusions is best supported by the statements above?
- The statements above, if true, best support which of the following conclusions?
- The author is arguing that
- Which of the following conclusions can most properly be drawn from the information above?
As mentioned earlier, an assumption is a piece of evidence that is not stated. It is something that the author of the argument is taking for granted when reasoning from the stated argument to the stated conclusion.
Here is an assumption question similar to those found on the GMAT:
Traditionally, decision making by doctors that is carefully, deductively reasoned has been considered preferable to intuitive decision making. However, a recent study found that senior surgeons used intuition significantly more than did most residents or mid-level doctors. This confirms the alternative view that intuition is actually more effective than careful, methodical reasoning.
The conclusion above is based on which of the following assumptions?
- Methodical, step-by-step reasoning is inappropriate for making many real-life medical decisions.
- Senior surgeons have the ability to use either intuitive reasoning or deductive, methodical reasoning in making decisions.
- The decisions that are made by mid-level and entry-level doctors can be made as easily by using methodical reasoning as by using intuitive reasoning.
- Senior surgeons use intuitive reasoning in making the majority of their decisions.
- Senior surgeons are more effective at decision making than are mid-level doctors.
The correct answer, E, provides a missing link in the author's reasoning by making a connection from the evidence: that intuition is used more by senior surgeons than other, less-experienced doctors, and the conclusion: that, therefore, intuition is more effective. None of the other choices helps bridge this gap in the chain of reasoning. Although some of the other statements may be true, they are not responsive to the question. In fact, they mostly focus on irrelevant factors such as appropriateness, ease of application, ability, or whether the doctors in question use the technique in a majority of their decisions.
Following are some other question stems that GMAT uses to indicate assumption questions:
- The official’s conclusion logically depends on which of the following assumptions?
- The conclusion above would be more reasonably drawn if which of the following were inserted into the argument as an additional premise?
- The argument above assumes that
- The conclusion drawn in the first sentence depends on which of the following assumptions?
- The conclusion of the above argument cannot be true unless which of the following is true?
The GMAT also includes questions that ask you to weaken or strengthen an argument. Most of the time, you are expected to choose the answer that either attacks or supports an assumption inherent in the argument. It is much less likely that you will find a correct answer that directly contradicts evidence that is stated in the argument. Our suggested technique is the same for both weakening and strengthening questions: First, identify the stated conclusion. Then, identify the stated evidence. Next, look for missing links that must be completed in order to create a strong chain of reasoning. If you are looking for the choice that weakens the argument, you need an answer choice that makes that assumption less likely to be true. Conversely, if you are trying to strengthen the argument, you need a choice that makes the assumption more likely to be true. The correct choice will not always completely disprove the conclusion or make it certain. There is a bit of subtlety required to get a maximum score on these questions.
The following is an example of a weakening question:
A drug that is very effective in treating some forms of cancer can, at present, be obtained only from the bark of the raynhu, a tree that is quite rare in the wild. It takes the bark of approximately 5,000 trees to make one pound of the drug. It follows, then, that continued production of the drug must inevitably lead to the raynhu's extinction.
Which of the following, if true, most seriously weakens the above conclusion?
- The drug made from raynhu bark is dispensed to doctors from a central authority.
- The drug made from the raynhu bark is expensive to produce.
- The leaves of the raynhu are used in a large number of medical products.
- The raynhu can be propagated from cuttings and cultivated by farmers.
- The raynhu generally grows in largely inaccessible places.
The correct answer, D, provides an alternate source of the raynhu bark. Even though the tree is rare in the wild, the argument is silent on the availability of cultivated trees. The author of the argument must be assuming that there are no raynhu trees other than those in the wild, in order to make the leap from the stated evidence to the conclusion that the raynhu is headed for extinction. So, to correctly weaken the argument, the test makers require you to attack an important assumption. The other answer choices all contain information that is irrelevant. Note that the correct choice does not make the conclusion of the argument impossible. In fact, it is possible that there may be domesticated raynhu trees and the species could still become extinct. Answer choice D is correct because it makes the conclusion about extinction less likely to be true.
Here are some other question stems that the GMAT uses to indicate weakening questions:
- Which of the following, if true, would most seriously undermine the conclusion drawn in the passage?
- Which of the following, if true, is the most appropriate reason for residents not to participate in the program?
- Which of the following, if true, would cast the most doubt on the accuracy of the group’s contention?
- Which of the following, if it were discovered, would be pertinent evidence against the speculation above?
- Each of the following, if true, weakens the conclusion above EXCEPT
The following is an example of a strengthening question:
Three years after the Hydraulic Falls Dam was built, none of the six fish species native to the area was still reproducing adequately in the river below the dam. Because the dam reduced the average temperature range of the water from approximately 40° to approximately 10°, biologists have hypothesized that sharp increases in water temperature must be involved in signaling the affected species to begin their reproduction activities.
Which of the following statements, if true, would most strengthen the scientists' hypothesis?
- The native fish species were still able to reproduce in nearby streams where the annual temperature range remains approximately 40°.
- Before the dam was built, the river annually overflowed its banks, creating temporary backwaters that were used as breeding areas for the local fish population.
- The lowest temperature ever recorded in the river prior to dam construction was 30°; whereas the lowest recorded river temperature after construction was completed has been 40°.
- Nonnative fish species, introduced after the dam was completed, have begun competing with the native species for food.
- Five of the species of fish native to the dam area are not known to be native to any other river.
The correct answer, A, most strengthens the conclusion that the scientists reached. It does so by showing that there is a control group. In other words, a similar population, not subjected to the same change as the population near the dam, did not experience the same type of result. This type of thinking is often referred to as the scientific method. It is often tested on the GMAT on problems that do not always involve scientific material. It is relevant to any time when there is a cause-effect relationship. Remember all that you learned about control groups and isolating variables. It will help you reason your way through this type of question.
Note that this question also adheres to the principal stated previously; you will usually attack or support assumptions when weakening or strengthening arguments. In this case, you are rewarded for choosing the answer that supports the assumption that the scientists must be making, which is, "If the dam had not altered the annual temperature variation in the river, the fish would be reproducing as they had before." In other words, they must be assuming that nothing else caused the lack of reproduction.
As with the weakening question above, the answer to this strengthening question does not prove the scientists’ conclusion once and for all. It does make it more likely that the conclusion is correct.
Here are some question stems that GMAT uses to indicate strengthening question stems:
- Which of the following, if true, would most significantly strengthen the conclusion drawn by the researchers?
- Which of the following, if true, could proponents of the plan above most appropriately cite as a piece of evidence for the soundness of their plan?
- Which of the following, if true, would most support the claims above?
- Which of the following, if true, would most strongly support the position above?
- Which of the following, if true, most strongly supports the hypothesis?
Some GMAT Critical Reasoning questions ask you to evaluate an argument. These questions are closely related to assumption, weakening, and strengthening questions. The correct answer identifies a question that must be answered or information that must be gathered to determine how strong the stimulus argument is. The information will be related to an assumption that the author is making. For example:
Although dentures produced through a new computer-aided design process will cost more than twice as much as ordinary dentures, they should still be cost effective. Not only will fitting time and X-ray expense be reduced, but the new dentures should fit better, diminishing the need for frequent refitting visits to the dentist's office.
Which of the following must be studied in order to evaluate the argument presented above?
- The amount of time a patient spends in the fitting process versus the amount of money spent on X-rays
- The amount by which the cost of producing dentures has declined with the introduction of the new technique for producing them
- The degree to which the use of the new dentures is likely to reduce the need for refitting visits when compared to the use of ordinary dentures
- The degree to which the new dentures are more carefully manufactured than are ordinary dentures
- The amount by which the new dentures will drop in cost as the production procedures become standardized and applicable on a larger scale
The correct answer, C, highlights an assumption in the stimulus argument. It shows that the author must be assuming that the reduction in refitting with the new dentures compared to ordinary dentures is significant in order to conclude that that difference will help offset an initial outlay that is twice as much. In other words, if you answer the question posed by answer choice C with "not much," the argument is weakened. If you answer it with "a tremendous amount," the argument is strengthened. The other answer choices are all irrelevant because no matter what the answers are, there is no impact on the relationship between the evidence presented in the stimulus argument and its conclusion.
Here are some other question stems that GMAT uses to indicate evaluation questions:
- Which of the following investigations is most likely to yield significant information that would help to evaluate the researcher’s hypothesis?
- To evaluate the argument above, it would be most useful to compare X and Y with regard to which of the following characteristics?
Another type of question that you will encounter asks you to identify a flaw in the stimulus argument. The question tells you that there is a problem with the logic of the argument. You just have to choose the answer that describes the flaw. Consider the following example:
Some observers have taken the position that the recently elected judge is biased against men in divorce cases that involve child custody. But the statistics reveal that in 40% of such cases, the recently elected judge awards custody to the fathers. Most other judges award custody to fathers in only 20%30%of their cases. This record demonstrates that the recently elected judge has not discriminated against men in cases of child custody.
The argument above is flawed in that it ignores the possibility that
- A large number of the recently elected judge's cases involve child custody disputes.
- Many judges find objectivity in child custody cases to be difficult to achieve.
- The recently elected judge is prejudiced against men in divorce cases that do not involve child custody issues.
- The majority of the child custody cases that have reached the recently elected judge's court have been appealed from a lower court.
- The evidence shows that men should have won custody in more than 40% of the recently elected judge's cases involving divorcing fathers.
The correct answer, E, points out a flaw in the argument. Specifically, it points out that the author of the argument was comparing the recently elected judge to other judges, not to the evidence presented in the recently elected judge's cases. In other words, the author of the argument made an unwarranted assumption that the recently elected judge did not rule against many men in custody battles where the evidence clearly favored the men. As with strengthening and weakening questions, the correct answer in flaw questions often involves unwarranted assumptions.
Here are some other question stems that GMAT uses to indicate a flaw question:
- The manufacturer’s response is flawed as a refutation of the consumer advocate’s argument because it
- Which of the following points to the most serious logical flaw in the author’s argument?
- The argument is flawed in that it ignores the possibility that
- Which of the following indicates a flaw in the reasoning above?
Some GMAT questions ask you to resolve a paradox, which is an apparent contradiction or discrepancy. In other words, there are two facts that are both true, and yet they appear to be in direct conflict with one another. For example:
Town Y is populated almost exclusively by retired people and has almost no families with small children. Yet Town Y is home to a thriving business specializing in the rental of furniture for infants and small children.
Which of the following, if true, best reconciles the seeming discrepancy described above?
- The business specializing in the rental of children's furniture buys its furniture from distributors outside of Town Y.
- The few children who do reside in Town Y all know each other and often stay over night at each other's houses.
- Many residents of Town Y who move frequently prefer to rent their furniture rather than buy it outright.
- Many residents of Town Y must provide for the needs of visiting grandchildren several weeks a year.
- Children's furniture available for rental is of the same quality as that available for purchase.
The correct answer, D, explains why a town of mostly retired residents might need to rent children's furniture. The other answer choices all contain irrelevant information. This further illustrates the fact that, on all question types, if you eliminate the irrelevant choices, the remaining choice will most likely be correct.
Here are some other question stems that GMAT uses to indicate paradox questions:
- Which of the following, if true, best reconciles the seeming discrepancy described above?
- Which of the following, if true, would best explain the opposition of X to the proposed law?
- Which of the following, if true, best explains the discrepancy above?
- Which of the following, if true, most helps to resolve the apparent paradox?
- Which of the following, if true, most helps to resolve the paradox outlined above?
The last type of Critical Reasoning question that we'll cover is the parallel structure question. In this type of question, you must choose the answer that has the same structure as the stimulus argument. In other words, you have to find the argument that is analogous to the given argument in that it includes the same relationship between the evidence presented and the conclusion. For example:
It is true that it is against international law to provide aid to certain countries that are building nuclear programs. But, if Russian companies do not provide aid, companies in other countries will.
Which of the following is most like the argument above in its logical structure?
- It is true that it is against United States policy to negotiate with kidnappers. But if the United States wants to prevent loss of life, it must negotiate in some cases.
- It is true that it is illegal to sell diamonds that originate in certain countries. But there is a long tradition in Russia of stockpiling diamonds.
- It is true that it is illegal for an attorney to participate in a transaction in which there is an apparent conflict of interest. But, if the facts are examined carefully, it will clearly be seen that there is no actual conflict of interest in the defendant's case.
- It is true that it is against the law to steal cars. But someone else certainly would have stolen that car if the defendant had not done so first.
- It is true that company policy forbids managers from making personal loans to employees without advance clearance from at least one vice president. But there have been many managers who have disobeyed this policy.
The correct answer, D, has the same structure as the stimulus argument. If you just replace "aid to developing nuclear powers" with "car theft," and "Russian companies" with the "defendant," it is essentially the same argument. Sometimes the parallel structure is easier to see if you use symbols to represent the terms of the argument: It is true that X is illegal. But, if Y doesn't do it, others will. Granted, the stimulus argument is in the future tense and the credited answer is in the past tense. However, it certainly is most like the stimulus.
Note that the answer choices that deal with the United States and Russia are not credited. This is a common characteristic of the parallel structure questions. The answer choices that contain the same or similar terms as the stimulus argument are rarely correct.
Here are some other question stems that GMAT might use to indicate parallel structure questions:
- Which of the following arguments proceeds in the same way as the above argument?
- Which of the following conclusions is supported in the same way as the above conclusion?
- Which argument below contains the same flaw as the argument above?
- Which of the following has the most similar structure to the argument above?
- Each of the following is similar in structure to the above EXCEPT