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#36350
Complete Question Explanation

Question #9: Must Be True. The correct answer choice is (D)

This stimulus presents a number of facts about microchips, but the author makes no argument and,
thus, draws no conclusion. This computer scientist discusses the various advances, in both speed and
cost, that have been brought to the microchip industry. Over the past several decades the number of
microchip transistors that are used on newly produced computer chips has doubled every eighteen
months. This served to double the microchips’ computing speed eighteen months as well. And during
the period from the mid-90s into the next decade, the cost of production of each microchip doubled
as well.

The question stem is a Must be True, which is not surprising, given that the stimulus is a simple
fact set. The right answer must pass the Fact Test, which means that it can be confirmed by the
information presented in the stimulus.

Answer choice (A): Very often in Logical Reasoning, and particularly on Must Be True questions,
incorrect answer choices can be ruled out based on a single word or phrase. This answer choice, for
example, can be ruled out based on the use of the term “only.” According to the stimulus, doubling
the number of transistors per microchip was clearly one effective way to double the computing speed
of the microchips, but that does not necessarily mean that doing so was the only effective way. The
scientist does not say that there are no other ways to double the computing speed of microchips, so
this choice cannot be confirmed by the information in the stimulus, fails the Fact Test, and cannot be
the right answer.

Answer choice (B): If this answer choice was appealing, that might be because you brought outside
information to the analysis. The scientist does not discuss the retail cost of computers, though, so this
choice cannot pass the Fact Test; since it cannot be confirmed by the facts in the stimulus, this cannot
be the right answer.

Answer choice (C): The costs associated with microchip production seems to have been increasing
quite quickly (doubling every 18 months seems impressive), but that does not necessarily mean that
nothing was done to control those costs. (it’s possible that cost control efforts were constant, and
that without them costs would have increased by even more) In any case, the issue of cost control
efforts is never mentioned in the author’s discussion of microchip production and costs presented in
the stimulus, so this choice fails the Fact Test and cannot be the right answer to this Must be True
question.

Answer choice (D): This is the correct answer choice. As we know from the stimulus, during the
last few decades the number of transistors on each microchip has been doubling every 18 months,
and that from the mid-1990s into the next decade, there was also a doubling of microchip production
costs every 18 months.

Answer choice (E): The computer scientist only discusses the trends from the past several decades,
and makes no claims about the future of the costs associated with increases to computer speed, nor
the likelihood that speed can be gained without increasing costs. Since there is no way to confirm
this choice from the facts provided in the stimulus, it cannot pass the Fact Test and should be ruled
out of contention.
 beniakc
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#3562
#9
Why is D the correct answer? IT is an Inference quesion and D is just a restatement of the stimulus. Why is C not correct?
 Nikki Siclunov
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#3572
This is a Must Be True question, requiring the application of the Fact Test: the correct answer choice must be proven by referring to the facts in the stimulus. Since we have evidence that the doubling in the cost of making new microchips accompanied each doubling of the number of transistors, we have sufficient proof that (D) is the correct answer choice.

Answer choice (C) is incorrect, because it is unclear whether engineers have (or have not) made attempts to control the cost of producing microchips. It's entirely possible that they did make an attempt to control their cost, but failed. This answer choice falls outside the scope of the fact set, and is therefore incorrect.
 beniakc
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#3577
Ahhhhh. I saw infer and thought assumption. Stupid mistake.
 jiyounglee
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#28492
would D be mistaken reversal?

Conclusion: each such doubling in a microchip's computing speed was accompanied by a doubling in the cost of producing that microchip

doubling in a microchip's computing speed :arrow: doubling in the cost of producing that microchip.

however, answer choice D says

doubling in the cost of fabricating new computer microchips :arrow: each doubling in the number of transistors on those microchips.

are we allowed to have a relationship of :dbl: instead of :arrow: because of "accompanied"?
 David Boyle
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#28585
jiyounglee wrote:would D be mistaken reversal?

Conclusion: each such doubling in a microchip's computing speed was accompanied by a doubling in the cost of producing that microchip

doubling in a microchip's computing speed :arrow: doubling in the cost of producing that microchip.

however, answer choice D says

doubling in the cost of fabricating new computer microchips :arrow: each doubling in the number of transistors on those microchips.

are we allowed to have a relationship of :dbl: instead of :arrow: because of "accompanied"?

Hello jiyounglee,

Yes, there could be a biconditional arrow, though that's not what's necessarily going on here. "Accompanied" is sort of a loose concept, which could go with conditional reasoning, causal reasoning, or just being a correlation. (Or maybe even a sheer coincidence, in some cases)
Overall, then, there may not be a mistaken reversal here. (Especially since D is the correct answer!)

Hope this helps,
David
 mshaikh
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#39041
Hello!

I wasn't sure about answer choice D because of the word "fabricating." In this context are they referring to people stealing the designs and making them. How can we know anything about fabrication from the stimulus? There was no mention of this. Initially when I did this question I was tempted to rule out all the AC's. I didn't like C because of the phrase, "without making any attempt..." And when I got to D I was so confused when I saw the word "fabricating" so I left it as a contender. I cancelled out all the other AC's but how can D be correct when it is introducing new information? I was thinking that fabricating microchips might not be too out of scope for this question. Please let me know!

Best,

Maham S.
 AthenaDalton
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#39360
Hi Maham,

Here, "fabricating" actually refers to "manufacturing," not stealing. :) Fabricate is a word that can have two meanings, and in this question the less-common meaning (to construct or manufacture) was being used.

Thanks for your question, and best of luck studying!

Athena Dalton

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