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Complete Question Explanation

Parallel Flaw. The correct answer choice is (C)

In this stimulus, the author uses historical rainfall data to predict the weather. Typically, we are
told, a few inches of rain fall in the valley each summer. This summer, however, no rain has fallen
there, and the summer is almost over, with only one week left. Based on this information, the author
concludes that “it will probably rain in the valley in the next week.”

The question stem identifies this as a Parallel Reasoning—Flaw question. Our job is to find the
answer choice that has the same flawed logical structure as the argument in the stimulus. In the
stimulus, the author committed a Time Shift error, assuming that because it usually has been the
case in the past that it probably will be the same way now. In the context of the stimulus, because it
usually rains a few inches in the valley during the summer, it probably will rain in the next week.

This argument lends itself to a quick abstraction, and so you could go through the answer choices
with the overall abstraction of the argument as your primary test. However, be aware that you can
test the conclusion of each answer choice fairly simply as well, since the conclusion must tell you
that something will probably occur.

Answer choice (A): This answer choice is incorrect because its conclusion says that there “may
be errors” in the unchecked pages. This conclusion is valid and does not match the probabilistic
conclusion in the stimulus. The conclusion here is valid because the fact that there are sometimes
errors in an issue of the journal tells us that such errors are possible, thus supporting the conclusion
that there may be errors in this issue.

Answer choice (B): This answer choice is inconsistent with the structure of the argument in the
stimulus because it concludes that there probably are no errors in the unchecked pages, despite the
fact that there are generally some errors—if there are generally few errors then it generally is the
case that there is at least one error—in each journal and she has not yet found any errors in this issue.

Answer choice (C): This is the correct answer choice because the its argument has the same
logical structure as the argument in the stimulus. The “few errors” in the typical journal issue are like
the “few inches of rain” that fall each summer in the valley. Since Aisha has not yet found any errors,
i.e., like there has not yet been any rain in the valley this summer, the argument concludes that there
are probably errors in the last few pages, just like the stimulus author concludes that it will probably
rain during the last week of the summer.

Answer choice (D): While this answer choice is the most attractive incorrect answer choice, it is
wrong because it talks about the probability of errors in the next issue of the journal as opposed
to the probability of errors in the remaining pages of this issue. In the context of the stimulus, this
structure would result in the argument that since it typically is the case that a few inches of rain fall
each summer and no rain has fallen this summer, then it will likely rain next summer.

Answer choice (E): Here, the conclusion does not match the conclusion in the stimulus, because it
tells us that Aisha “probably made a mistake.” To match this answer choice, the stimulus would have
to reach the conclusion that the person measuring the rainfall has probably made a mistake in that
  • Posts: 97
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Hi, sorry for posting so many questions, I appreciate the explanations a lot...

So for this question, I know it's flaw to estimate something could happen based on past experience,
but for some questions (cannot remember which) that ask which could work as strengthener/weakener, the author uses past experience to predict what would happen in future...
I would like to know the difference between this question and those ones...the one ppl can use such statements as strengthener or weakener.

 Adam Tyson
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This one isn't so much about using the past to predict the future, but about using what is usual (let's call that an average) to predict an outcome in a specific instance. The author argues that since there is a known average, this particular instance can be expected to conform to that average. That, of course, doesn't have to be true - what is usual (the average) need not happen in every single case, and in fact the use of the words "usual" and "average" suggest that it may occur less than 100% of the time and that there may be some fluctuation around that average or norm.

An acceptable use of the past to predict the future in this case might look like answer A here, which doesn't predict that there will probably be errors but instead says only that there may be errors. See the difference?
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I got lucky this time, but I was between A and C.

In C, it says "on average a few"

Is "on average a few" same as "usually"?

aren't they different? I thought they were, which made me confused. "usually" means "more than half." I don't think "on average a few" means "more than half."

Thank you!
 Adam Tyson
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"On average" would be the part that matches the "usually" idea, Jay! The "a few" is just what usually happens, just like in the stimulus where there is usually "a few inches" of rain. It's not that "usually" and "a few" conflict with each other, but that they both have the same idea of "usually there are a few." Think of that as "most of the time there is some small amount."

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