- PowerScore Staff
- Posts: 902
- Joined: Oct 19, 2022
- Tue Jan 14, 2025 1:07 pm
#111466
Hi Ricky,
Actually, using the Double-Not Arrow was completely appropriate and both your diagram of the stimulus and Answer C were correct. The stimulus does directly state that "good pets" and "poison fangs" never go together, which can be diagrammed using the Double-Not Arrow or in the regular form (GP -> ~PF).
That being said, I find that some students struggle making inferences when using the Double-Not Arrow in conditional/formal logic chains (for example, they forget to apply the negative sign), so feel free to diagram it without the Double-Not Arrow if that's easier. Fortunately, you remembered to apply the negative sign when making your inference, and that inference was correct.
Where you went wrong is actually in the conclusion of Answer C and comparing what it actually says to the inference that you made.
Your inference for Answer C, which was correct, was:
RM
~Collection
In plain English, this means that "There are some poems with regular meter that are not in this collection."
Unfortunately, that is not what the conclusion of Answer C states, although the wording is quite tricky.
Answer C concludes "Not all of the poetry in this collection has a regular meter."
"Not all" means "some are not," so we can reword this conclusion to "Some of the poetry in this collection does not have a regular meter."
This would be diagrammed:
Collection ~RM
See the difference between this and the inference that you made? The key is which term is positive and which term is negative, and these two statements/diagrams are not saying the same thing.
Actually, using the Double-Not Arrow was completely appropriate and both your diagram of the stimulus and Answer C were correct. The stimulus does directly state that "good pets" and "poison fangs" never go together, which can be diagrammed using the Double-Not Arrow or in the regular form (GP -> ~PF).
That being said, I find that some students struggle making inferences when using the Double-Not Arrow in conditional/formal logic chains (for example, they forget to apply the negative sign), so feel free to diagram it without the Double-Not Arrow if that's easier. Fortunately, you remembered to apply the negative sign when making your inference, and that inference was correct.
Where you went wrong is actually in the conclusion of Answer C and comparing what it actually says to the inference that you made.
Your inference for Answer C, which was correct, was:
RM
~CollectionIn plain English, this means that "There are some poems with regular meter that are not in this collection."
Unfortunately, that is not what the conclusion of Answer C states, although the wording is quite tricky.
Answer C concludes "Not all of the poetry in this collection has a regular meter."
"Not all" means "some are not," so we can reword this conclusion to "Some of the poetry in this collection does not have a regular meter."
This would be diagrammed:
Collection
~RMSee the difference between this and the inference that you made? The key is which term is positive and which term is negative, and these two statements/diagrams are not saying the same thing.
