CR Made Easy

ASSUMPTION QUESTIONS

The most basic type of Critical Reasoning question asks you to identify an assumption of the argument. A question of this type might have the following wording:
1. Which of the following is an assumption that enables the conclusion above to be
properly drawn?
2. Which of the following is an assumption made in drawing the conclusion above?
3. The conclusion of the argument above cannot be true unless which of the
following is true?
4. Any of the following, if introduced into the argument above as an additional
premise, makes the argument above logically correct EXCEPT

Assumption questions ask you to examine the relationship between the premise and the conclusion in an argument, and to determine what other conditions are necessary in order for the argument to be valid. In the example given about Dora’s house surviving the earthquake, the correct answer will need to bridge the logical gap between the statement “Dora’s house meets the building code” and the conclusion “Dora’s house will survive the next earthquake.” The answer will be some variant on

Houses that meet the building code will survive the next earthquake.

Note that the specific wording of the question will determine the specific wording that is acceptable for the answer. For example, if the question asks, “Which of the following is an assumption made in drawing the conclusion above?” then a statement like “The building code contains provisions that help protect houses from earthquake damage” could be sufficient. However, if the question asks, “Which of the following is an assumption that enables the conclusion above to be properly drawn?” then this relatively noncommittal statement would be insufficient, because it alone is not sufficient to prove that Dora’s
house necessarily will survive the earthquake. Critical Reasoning questions often hinge on the fine meaning of individual words, so always read the passages carefully, and read the question stems very carefully.


WEAKEN THE ARGUMENT

The most common type of Critical Reasoning question by far is the weaken-the-argument question. If the argument in the passage is a stool held up by assumptions, then this type of question asks you either to locate the spot where a leg is missing or to kick a leg out from under the stool. These questions could have the following wording:

1. Which of the following, if true, would most weaken the conclusion above?
2. Which of the following, if true, most severely undermines the argument
presented above?
3. Which of the following, if true, most clearly points to a flaw in the manufacturer’s
plan?

The thinking required here is very similar to that required for an assumption question, but you have to take it a step further. With these questions, you determine what assumptions have to be true in order for the argument to be true, and then find the answer that challenges one of those assumptions.

For example, consider the following:

Earthquakes often destroy houses that are not built according to the building code. Dora’s house was built according to the building code, so it will survive the next earthquake.

In this argument, there are two premises:
Premise 1: Earthquakes often destroy houses that are not built according to the
building code.
Premise 2: Dora’s house was built according to the building code.
And one conclusion: Therefore, Dora’s house will survive the next earthquake.

In the example of Dora’s house, a correct answer could look like one of these:
1. When the last major earthquake occurred in the area, many houses that met
the building code were destroyed.
2. Geologists predict that the coming earthquake will be far more severe than any
earthquake previously recorded in the area.
3. The building code in Dora’s area is designed exclusively to protect homes
against flood and fire damage.

Each of these answers kicks at the assumptions holding up the conclusion, thereby weakening the argument. The thinking here is similar to the kind of thinking you use every day when you evaluate arguments: you look for flaws in the argument, and you consider ways in which the plan might not work exactly as promised.
When answering these questions, be careful not to pick an answer that actually strengthens the argument. These answers are tempting because they often deal with the same themes as answers that weaken the argument, but they use slightly different wording that produces the opposite effect. GMAT usually puts at least one answer choice like this in every weaken-the-argument question.


STRENGTHEN THE ARGUMENT

Strengthen-the-argument questions use very similar thinking to weaken-the-argument questions, but instead of kicking the assumptions out from under the argument, you are asked to prop them up. This type of question comes up perhaps half as often as weaken-the-argument questions.

Strengthen-the-argument questions could have the following wording:
Which of the following, if true, would most significantly strengthen the conclusion drawn in the passage?
Which of the following, if true, offers the strongest support for the manager’s conclusion that the locks were not at fault?
Which of the following, if true, provides the strongest evidence in favor of the professor’s hypothesis?

For example, consider the following:

Earthquakes often destroy houses that are not built according to the building code. Dora’s house was built according to the building code, so it will survive the next earthquake.

In this argument, there are two premises:
Premise 1: Earthquakes often destroy houses that are not built according to the
building code.
Premise 2: Dora’s house was built according to the building code.
And one conclusion: Therefore, Dora’s house will survive the next earthquake.

In the case of Dora’s house and the earthquake, you must look for a statement that confirms one of the assumptions upon which the conclusion rests. Strengthening answers for that question might look like this:

In the last earthquake, no buildings that met the building code were severely damaged, although several substandard buildings collapsed.
Geologists predict that the next earthquake will be so minor that no damage is expected for any building in the area.
The local building code was designed by architects who used data from previous earthquakes in the area to determine the best ways to protect homes from earthquake damage.

Each of these answers addresses potential flaws in the argument—the same flaws that a weaken-the-argument question would try to exploit. Remember, most of these arguments could go either way, and you need to be careful to make sure that the answer you choose points in the desired direction. As with weaken-the-argument questions, strengthen-the-argument questions almost always have at least one answer that deals with the correct subject matter, but in a way that is actually the opposite of what the question asks for. Don’t be fooled.

Note that the correct answer to a strengthening question does not necessarily have to prove that the argument is correct. An answer that eliminates a single potential flaw in the argument could be the correct answer, as long as it is the best among the available answer choices.


INFERENCE QUESTIONS

Inference questions ask you to make a logical inference based on the information presented in the passage. The wording of these questions can vary widely, but the basic question behind them is the same: if the statements in the passage are true, what else has to be true? Assumption questions are actually a specific kind of inference question that asks: if the argument is valid, you can infer that which of the following assumptions must be true in order to logically connect the premise and the conclusion? The same type of critical thinking is used for both assumption and inference questions, but the nature of the inference is slightly different. The inferences discussed here are not necessarily vital components of the argument, but rather logical extensions from it; in the metaphor of the stool, if you kicked over one of these inferences, the stool would not necessarily topple over. Inference questions might relate to the assumptions of an argument, to its premise, to its conclusion, or to its application to a related situation. Questions of this type might look like this:

If the statements above are true, which of the following must be true?
The statements above, if true, best support which of the following assertions?
Which of the following can be correctly inferred from the statements above?
If the statement above is true, then what outcome could be expected in a fight between a bear and a lion?

The key to answering these questions correctly is to keep your logic very tight. The writer of the argument can make unsupported assumptions, but you cannot. The correct answer will be a small logical hop, not a leap, from the statements in the passage. Many test takers are surprised by how reserved the correct answers for inference questions usually are, because they expect the correct answer to be a bolder statement. Do not expect a bold answer. The correct answer will usually be a very moderate statement, and it will be the only one that has to be true if the statements in the passage are true.

Let’s consider an example with Dora’s imperiled house:
Earthquakes often destroy houses that are not built according to the building code. Dora’s house was built according to the building code, so it will survive the next earthquake.
In this argument, there are two premises:
Premise 1: Earthquakes often destroy houses that are not built according to the
building code.
Premise 2: Dora’s house was built according to the building code.
And one conclusion: Therefore, Dora’s house will survive the next earthquake.

Many houses that do not meet the building code will collapse in the next earthquake. The foundation of Dora’s house contains the structural stabilizers required by the building code, so her house will survive the earthquake.

There are a few valid inferences that you can draw from this statement:

Houses that do not meet the building code do not necessarily contain structural stabilizers.
Structural stabilizers play a role in protecting houses from earthquake damage.
Houses that do not contain structural stabilizers have a higher chance of being damaged in an earthquake than houses that contain these stabilizers.

Note that these inferences, while valid, do not all have to be true in order for the conclusion
“Dora’s house will survive the earthquake” to be true. Note also the moderate tone of the inferences. It is easier to establish that structural stabilizers “play a role in protecting houses” than that they “protect houses from all damage.” Phrases like not necessarily and have a higher chance help create the weak claims that GMAT tends to favor in this type of question. Remember, it is easier to prove that a weak claim must be true than that a strong claim must be true, so ACT usually relies on weak claims.
One method that many strong test takers use to evaluate answer choices for this type of question is to ask, what if the opposite of this answer were true? A correct answer will always make sense within the context of the passage, whereas the opposite of the statement generally will not. If a statement and its opposite both make equally good sense in the context of a sentence, then it probably is not the correct inference. Practice this technique with the inferences given earlier to see how it works; in every case, the opposite statement runs contrary to the sense of the passage.


Explain/Resolve the Discrepancy

Sometimes the arguments in Critical Reasoning passages will leave some ends clearly untied. They may present information that is confusing, or even contradictory, when taken on its own. The question will then ask you to provide a logical explanation that resolves the confusion.

Questions of this type could look like this:
Which of the following, if true, would best explain the sudden increase in productivity described above?
Which of the following, if true, best accounts for the fact that ethanol is not widely used in internal combustion engines?
Which of the following, if true, would help to explain the discrepancy described above?

The reasoning for these questions is actually quite similar to the reasoning used for assumption questions. Explanation questions often present you with a premise and a conclusion that seemingly do not work together, and you need to find the assumption that connects the two in a logical way.

For example, consider the following passage:
Over the past year, Robert won several medals in running competitions. He was recently involved in a minor automobile accident, however, and as a result of his injuries, he currently is required to wear a cast. Despite this fact, he is favored to win the big race next month.

Which of the following would help to explain the apparent paradox described above?

You need to find the unstated assumption that could make the conclusion true in spite of the premise. A correct answer could be
Robert wears a light cast on his wrist that does not slow him when he runs.
The big race next month is a balloon race.
The cast will be removed next week, and doctors expect Robert to be fully recovered before the big race occurs.

Each of these statements, if true, could account for Robert’s favored status in the big race next month despite his cast and injuries. Before you look at the answers for a question of this type, always try to sketch out an idea of what the correct answer could look like. Jot down a short version of it on your scratch paper if that helps. The actual answer might take a very different direction from the one you sketched out, but the exercise of formulating an answer will help you to see the kinds of unstated assumptions that could fit between the premise and the conclusion.


Fill in the Blank


This type of question presents you with most of an argument, but leaves a blank space at the end, which you are asked to fill in. The blank space will usually represent the conclusion of the argument, but it could also represent a key premise. The wording for these questions will always be some variant of

Which of the following best completes the passage below?

These questions are really quite straightforward. Examine the argument in the passage. Determine whether it is the conclusion or a premise that is missing. Formulate the answer in your head, then look through the answers for the one that fits. For example, if you see a question that looks like

Which of the following best completes the passage below?
Over the past year, Robert was unbeaten in running competitions at the distances of 400 meters and 800 meters. He was recently involved in a minor automobile accident, however, and as a result of his injuries he is required to wear a cast that will significantly restrict his movement for the next six months. Consequently, when an important running competition of 400 meters is held next month, __________.

Explanation: The answer will be something on the order of “Robert will not be able to win the race” or, preferably, “Robert is unlikely to win the race”; the more moderate answer is usually the correct one. Look for the conclusion that the stated premises are directing you toward. In general, you should treat these questions the same as you would an inference-making question: keep your logic tight, and look for the answer that has to be true if the premises in the passage are true.



PS: This post is compiled from various sources. I have just put them all at one place for quick reference. Please press 'KUDOS' if this post helps you!