#11 - Inspector: The only fingerprints on the premises

[Administrator]

Complete Question Explanation

Parallel Flaw—CE. The correct answer choice is (A)

Your task in this Parallel Reasoning question is to select the answer that presents an argument
containing flawed reasoning most similar to that used by the inspector.

Premise: the only fingerprints on the premises are those of the owner, Mr. Tannisch

Conclusion: thus, whoever has his guest’s missing diamonds must have worn gloves

The inspector makes the mistake of inferring, without proper support, that the absence of fingerprints
other than that of the homeowner resulted from the use of gloves. While it may be the case that the
the thief wore gloves, that is not the only possible cause for the absence of any other fingerprints.
As with many LSAT stimuli, this argument has more than one weakness, but the causal flaw is most
central to the conclusion and therefore forms the basis of our prephrase.

The correct answer will present an argument with a similarly flawed use of causal reasoning. The
incorrect answers will not present an argument with this same type of flaw.

Answer choice (A): This is the correct answer choice. Like the argument in the stimulus, this
argument improperly infers from the identity of those who became ill that some cause other than
something the people ate must have caused the illness.

Answer choice (B): This choice is incorrect, because it does not contain a definitive conclusion
similar to that in the stimulus, in which the conclusion was that something “must” have been the
cause. The elimination of the choice based on the difference in language in the conclusions is called
the Double the Conclusion test.

Answer choice (C): This choice is incorrect because its conclusion is a determination of probability
based on prior performance, while the stimulus presented a flawed causal argument.
Answer choice (D): The argument in this choice prescribes a course of action, while the stimulus
presented a flawed causal argument.

Answer choice (E): This conclusion makes a prediction as to a probable outcome based on an
unsupported comparison, while the stimulus contained a flawed causal argument.

[melissa27]

Can you please explain question 11 on section one of the dec. 2011 exam?

[Adam Tyson]

Question 11 strikes me as being a little bit tougher. What's wrong with the Inspector's argument? Well, if we prephrase it, we might say that he failed to consider that Mr. Tannisch might himself have stolen the diamonds. Or, we might just say that he made an unwarranted assumption - that Tannisch didn't do it - without providing any justification for that assumption.

The problem, in my view, is that several answer choices seem to be based on unwarranted assumptions. Answer D, for example - the author there has assumed, without providing justification, that cavities appear more on the side where you chew than on the side where you don't. So why is A a better answer? I think it has to do with ignoring evidence - just like the Inspector ignored the evidence of Tannisch's fingerprints, the author in A has ignored the evidence of the common food source, the camp cafeteria. D lacks that element of evidence being ignored without explanation.

That's my take on it, anyway. Perhaps one of my colleagues will add their two cents?

Good luck, Melissa!

Adam M. Tyson
PowerScore LSAT Instructor

[Steve Stein]

I totally agree with Adam's explanation: the flaw found in both the stimulus and answer choice A is that in each case, the author presumes the innocence of a fairly obvious suspect without any particular justification for doing so.

[ericau02]

This makes sm more sense with the second explanation. My thought were exactly as adams thanks!!