there is a new train line that goes directly to the city

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What to Expect on the GMAT

2. there is a new train line that goes directly to the city

Clearly, the second explanation here is better. It can explain more phenomena, such as an increased demand for apartments, an increase in local property taxes, an increase in population, and an increase in upscale retail establishments in the area.

Consistent with well-established theory/common knowledge. Although established theories are not infallible (remember, people once thought the world was flat), you need very powerful evidence to dis-card them. So, if an explanation conflicts with such a theory, you have good reason to be suspicious.

Likewise, if an explanation conflicts with your common knowledge, be on guard. It is probably not a good one.

Example: That little girl has tons of freckles, just like her parents. They all must spend way too much time in the sun.

Although it’s true that sun exposure can cause some people to develop freckles, this explanation goes against the well-established theory of heredity. If a little girl has freckles and her parents also have freckles, it is safe to assume she inherited the freckle gene from her parents.

Returning to the bookstore question about the placement of romance novels, you can further assess the possible conclusions with these criteria for evaluating explanations. You could test all of the choices to see if they are correct, none are circular, and all have explanatory power. But a—that customers would come back for another romance novel—is not reliable or relevant to the scenario. Return purchases have nothing to do with the placement of books in the store.

Common Flaws in Causal Arguments

Arguments about cause (why things happen) contain their own types of fallacies that you should watch out for, including the following:

post hoc, ergo propter hoc

ignoring possible common cause

assuming common cause

reversing causation


Translated from Latin, this means “after this, therefore because of this.” This argument assumes that X caused Y just because X preceded Y. For example,

The problem with this argument is that although X (Thompson’s taking office) preceded Y (the mar-ket crash), that does not mean Thompson caused the marmar-ket crash. The key question to ask is this: Is X the only relevant change prior to Y? In this case, definitely not. Many, many other relevant factors could have pre-ceded the market crash. (Besides, it is difficult for a politician to destroy the economy “as soon as” he or she takes office. Common sense tells you it would take some time for a leader’s policies to have an impact.)


This argument assumes that X caused Y, but maybe X and Y were both caused by another factor (W). For example,

I had hives because I had a fever.

Perhaps the fever caused the hives, but maybe the hives and the fever were both caused by another fac-tor, such as a virus. Before accepting a causal explanation, ask the following: Could there be an underlying cause for both X and Y?


This argument assumes that X and Y had a common cause and ignores the possibility of a coincidence. Maybe X and Y are due to different or multiple causes. For example,

On Thursday, there was a black cat sitting in my driveway. That night, I had an accident in my car. On Friday, the cat was there again, and that night, my boyfriend broke up with me. That black cat sure brought me some bad luck.

Besides the fact that this argument does not have much initial plausibility (and requires belief in the superstition that black cats bring bad luck), it fails for several other reasons:

It ignores the possibility of coincidence.

It does not consider the fact that a black cat is totally irrelevant to the occurrences.

It does not consider other possible common causes (maybe the accident and the breakup were both due the speaker’s inability to pay attention—to the road and to her boyfriend).

It does not consider that the two events could have resulted from very different causes (the accident could have been because the speaker was distracted; the breakup could have been caused by an infi-delity, a change of heart, and so on).


This fallacy confuses cause and effect (the “chicken and the egg” problem), arguing that the effect was really the cause or vice versa. For example,


This example could definitely be a case of reversed causation. Maybe Lucy aced her last two exams because she was feeling more confident. You would have to study the situation further to determine which was cause and which was effect. If you suspect reverse causation, consider carefully whether a reversal of cause and effect could have occurred. Is it possible for the alleged cause to actually be an effect, or the effect to really be the cause?

Now take a look at the following question. Use your knowledge of causal argument fallacies to answer it correctly:

Did you ever notice that successful business people drive expensive cars? If I get myself an expensive car, I will become more successful.

The most serious flaw in this argument is

a. it assumes all successful business people drive expensive cars.

b. it reverses cause and effect.

c. it is not a testable explanation.

d. it ignores the possibility of coincidence.

e. it ignores a possible common cause.

The correct answer is b: The argument reverses cause and effect. Successful business people can afford expen-sive cars because they are successful; the success comes first, then the car. The speaker may be looking at some serious debt if he believes otherwise.

Sentence correction questions are designed to measure your knowledge of both grammar and effective style.

Chances are you already know most of these rules and guidelines even if you don’t know how to articulate them. You can often tell when something sounds wrong, even if you don’t know exactly why it is wrong. That is good news because on the GMAT® exam you do not have to identify the grammar rule that has been bro-ken or what makes the writing ineffective. Rather, you will simply have to identify which sentence is free of errors and written most effectively.

That said, you can still benefit a great deal from a review of the basic rules of grammar and guidelines for effective style, especially if you feel that grammar is not your strong suit. You may find some sections here more basic than you need, but give yourself the opportunity to review everything in this section. You may find that you have forgotten some rules and guidelines, and a review of the rules and terminology can give you more confidence on the exam.




24 Rules for Grammar and Style

Throughout this chapter, you will learn about and review each of these rules in depth. After you have completed the chapter, use the following list as a checklist as you review for the GMAT exam:

1. Follow the basic subject-predicate word order for sentences: subject, verb, indirect object, and direct

In document LearningExpress s EXAM SUCCESS GMAT. In Only 4 Steps! (Page 117-122)

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