#18 - Some planning committee members--those representing

[Robert Carroll]

conorrjohnston,

Let's examine each thing you diagrammed:

Planning Committee Members Sig Financial Interests

This is correct.

Planning Committee Members <-NONE I -> (X) Live in Suburbs

This diagram doesn't look right to me. You can make a "none" into a conditional or a Double-Not Arrow.

As a conditional:

planning committee member live in suburbs

As a Double-Not Arrow:

planning committee member live in suburbs

Planning Committee Members Work in Suburbs.

This isn't correct. "Many" does not mean "most". "Many" is usually, and definitely here, used as a "some" indicator. So the correct diagram is as follows:

planning committee member work in suburbs

This highlights the issue with answer choice (C). Some members have significant financial interests. Some members work in the suburbs. There's no reason for those to be the same members, though. The committee may have 10 members. 3 of the 10 have significant financial interests. 4 of the 10 work in the suburbs. There are enough members in the committee for there to be no overlap between these two subgroups.

The opposite problem exists with answer choice (D). What if the ones with significant financial interests, specifically the ones representing the construction industry, are the same as the ones who work in the suburbs? They could be!

So the problem with both answer choices is that they may be true, but also may not be. They thus don't meet the standards of a Must Be True question.

Robert Carroll

[bonbon94]

I am trying to understand the diagraming of this question, but all the different arrows are confusing to me still. I thought it was B or E, and I understand now that B is incorrect because not everyone with signifiant financial interest is on the planning committee so the answer is too strong.

But I am still confused on why we cannot assume if a person does or does not work in the suburbs like answers C and D state.

If no one on the comitte lives in the suburbs but some work there, why don't C and D work.

Also why is the use of "some" able to make the diagrams reversible? I am trying to understand the logic of this question, but it is stumping me

[Jeff Wren]

Hi bonbon,

This question involves formal logic. Formal logic is a difficult topic for many students and requires a thorough understanding of various concepts in order to correctly diagram the various logical statements and to correctly make the inferences. A full discussion/explanation of formal logic is beyond the scope of this forum. If you haven't done so already, I'd recommend reading (perhaps more than once, as it is rather complex) chapter 13 of "The Logical Reasoning Bible," which covers this topic in great detail.

Answer C attempts to link two terms that were both connected by "some" statements, which is not valid. For example, from the statement "Some Americans live in Texas and Some Americans live in Alaska," you cannot infer that "Some Americans who live in Texas also live in Alaska." These groups do not necessarily overlap.

As for Answer D, there is no term in the stimulus regarding people who do not work in the suburbs, only people who do work in the suburbs. You cannot infer anything about people who do not work in the suburbs based on the stimulus. Do not make the mistake of assuming that if some people do work in the suburbs, that implies that some people do not work in the suburbs. The word "some" in formal logic means "at least one," but could be anything from 1-100%.