LSAT and Law School Admissions Forum

Get expert LSAT preparation and law school admissions advice from PowerScore Test Preparation.

 Administrator
PowerScore Staff
  • PowerScore Staff
  • Posts: 8950
  • Joined: Feb 02, 2011
|
#84840
Complete Question Explanation

Parallel Flaw. The correct answer choice is (D)

The structure of the argument is very distinct: the two premises and conclusion each contain the
quantity indicator “most.” That structure must be paralleled in the correct answer choice, and you
would be wise to immediately check the answers upon recognizing the triple “most” formation. Let
us do so now:

Answer choice (A): The second line of the answer choice contains the phrase “very few.” Since this
is different from “most,” this answer is incorrect.

Answer choice (B): The answer choice contains the phrases “cannot” and “no one,” both of which
are different from “most.”

Answer choice (C): The phrase “usually” is a synonym for “most,” but the two “all” statements are
different enough to make this answer choice suspect.

Answer choice (D): This is the correct answer, and the only one with three “mosts.”

Answer choice (E): The second line contains a conditional premise (introduced by “only”). Since the
argument does not contain a similar premise, this answer is incorrect.

Amazingly, the application of this basic structural element solves the problem very quickly. The
question itself represents a perfect example of how you should attack Parallel Reasoning questions:
search for the most distinctive element, then use that element to eliminate as many answer choices as
possible. You will not always be lucky enough to eliminate all four incorrect answer choices at once,
but any answer you eliminate puts you one step closer to your goal.

For the record, the argument makes an error of division in assuming that a general proposition
about “most people” will apply to any subset of that group. In this case, “most people who shop for
groceries” could be about the entire United States, and within this group there could be towns and
cities such as Hallstown that do not conform to the general truth that applies to the whole.
 Nikki Siclunov
PowerScore Staff
  • PowerScore Staff
  • Posts: 1362
  • Joined: Aug 02, 2011
|
#27162
The argument is structured as follows:
  • Premise: Shop for groceries max. 3 times/month :most: Buy frozen dinners

    Premise: Hallston :most: Shop for groceries max. 3 times/month

    Conclusion: Hallston :most: Buy frozen dinners
There are several ways of looking at this logical flaw. First, it's an Error of Division. The statement "most people who shop for groceries no more than 3 times a month buy prepared frozen dinners regularly" is a statement about a class of people having a certain attribute. Since Hallston is a member of that class, the conclusion depends on the erroneous transference of the attribute from the class onto a member of that class. In other words, the argument assumes that a general proposition about “most people” will apply to any subset of that group. In this case, “most people who shop for groceries” could be about the entire United States, and within this group there could be town and cities such as Hallstown that do not conform to the general truth that applies to the whole.

It's also helpful to recognize this as a Formal Logic error. Just because most people in general do something doesn't mean that the people in Hallston will do it. After all, it's entirely possible that 49% of the people who shop for groceries no more than 3 times/month do NOT buy frozen dinners, and that everyone living in Hallston is part of that 49%. There is actually no conclusion we can draw about the people of Hallston: it's entirely possible that NONE of them buy frozen dinners regularly.

As a general rule of thumb, we cannot "cross" two :most: arrows in a chain (A :most: B :most: C) and expect to arrive at a logically valid deduction (A :most: C is not a valid conclusion).

Get the most out of your LSAT Prep Plus subscription.

Analyze and track your performance with our Testing and Analytics Package.