#23 - Every brick house on River Street has a front yard.

[Nikki Siclunov]

Hi Zierra28,

"Brick houses" and "houses" are indeed two different categories; however, the stimulus never talked about houses in general. The premises specifically entailed brick houses, and houses with front yards, all of which are supposedly on River Street:

• Premises: Brick House Front Yard Two Stories
  
  Conclusion: Brick House Two Stories

Clearly, the reasoning is flawed, because we don't know how many houses with Front Yards there are on River Street. If virtually all the houses have front yards, and only a few houses are made of brick, then it would be possible that no brick house has two stories.

To avoid the problem you were having, it is important to read the entire stimulus before setting out to diagram the relationships between the propositions.

Thanks,

[nowornever]

I understand the (flawed) logic behind this question, but does anyone have any tips on how to complete this question quickly? I went through and diagrammed all of the answer choices, but I don't feel like this will be a practical use of my time on test day. Does anyone have any suggestions on how to complete this type of question accurately and quickly?
As always, thanks!

[Robert Carroll]

now,

I will almost never diagram all of the answer choices for a Parallel Reasoning (or Parallel Flaw) question, precisely because of how long it takes. What I WILL do, if I can, is diagram the stimulus. Then I look at "distinctive" features of the stimulus reasoning, and check every answer choice against those.

Here, I notice that the stimulus has two premises, one an "every" statement (so, a conditional!) and one a "most" statement. Further, the conclusion is a "most" statement. So any answer that does not have parts with those features is out without needing a full diagram. I am NOT saying that an answer is wrong if it doesn't say the word "most" at all - there are many different words I could use to express a "most" relationship - but instead I am saying that an answer with parts not even logically equivalent to the parts in the stimulus can be eliminated.

Looking at my answers:

Answer choice (A): I see a premise with "all," a premise with "most," and a conclusion with "most". Keep this as a Contender.

Answer choice (B): I see a premise with "most" and another premise with "most". Get rid of this - the premises don't match up.

Answer choice (C): I see a conclusion with "not every," which is equivalent to a "some" statement. The stimulus's conclusion doesn't involve anything like that, so eliminate this answer.

Answer choice (D): This answer has a premise with "all," a premise with "most," and a conclusion with "most". Keep as a Contender.

Answer choice (E): Both premises have "most," so this answer is out.

Note how only two answers matched these properties of the stimulus, and how I didn't need to diagram the answers to make these judgments. I now have only two Contenders, and I can diagram one or both of THEM to decide what I should pick. There is no need to diagram more than just those two, because the other answers have been eliminated.

Robert Carroll