Question 7 on Either/Or sentence in stimulus

Why do we diagram the last sentence (either/or language) with a negated necessary statement instead of negating the sufficient?

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BenMingov November 11, 2019

Hi Saphi, thanks for the question!

I think this might just be a case of having a confusing double negative.

The statement is an either/or as we have established. Either unpopular with faculty or unpopular with students.

Either/or statements take the following form:

NOT A - > B
NOT B - > A

This occurs because if we don't have one then we need the other to satisfy the either/or requirement.

Now back to the example:

The example in the video used the shortened: PF (popular with faculty) and PS (popular with students)

To signify unpopular with faculty and unpopular with students, these would become:

NOT PF and NOT PS (these would appear crossed out in your diagram, rather than not)

To satisfy the either/or diagram:

It would become NOT NOT PF - > NOT PS
NOT NOT PS - > NOT PF

These simplify to what was shown in the video:

PF - > NOT PS
PS - > NOT PF

Hope this helps!