The statement is: All Labrador retrievers bark a great deal.
Labrador retrievers = L Bark a great deal = BGD
Positive statement: L ==> BGD Contrapositive: not BGD ==> not L [reversing & negating the positive]
Answer choice (B) is an incorrect reversal - it simply flips the given sufficient & necessary conditions, which is an error in reasoning.
Remember: you cannot just reverse a positive statement, nor just negate a positive statement. You must both reverse and negate a positive statement to obtain the contrapositive.
Hope this helps! Please let us know if you have any additional questions.
Hollie-MacCutcheonMay 21, 2018
Hi! Where can I find the lesson about how to answer these types of questions?
@Hollie-MacCutcheon, look at the Sufficient & Necessary section of the course. There will be a video walking you through it and also a series of drills related to this type of setup.
stevedpdAugust 4, 2019
That argument doesn't make sense to me. That like saying all owls are birds. Then making it contrapositive would say if you aren't an owl you aren't a bird.
VictoriaAugust 4, 2019
Hello, thanks for your post!
Remember that you cannot simply reverse nor simply negate a S&N statement to make it the contrapositive.
For the above example, the passage states: "All Labrador retrievers bark a great deal."
Therefore, if you are a Labrador retriever, you bark a great deal. L - > BGD
It follows then that if you do not bark a great deal, you cannot be a Labrador retriever. Why? Because if you are a Labrador retriever, you bark a great deal.
This is the contrapositive (i.e. the reversal and negation of the original S&N statement).
L - > BGD Not BGD - > Not L
For your example about owls, the S&N statement would be "all owls are birds."
O - > B
However, you did not reverse the contrapositive, you simply negated it. The correct contrapositive would be if you aren't a bird, you aren't an owl. This is because all owls are birds; therefore, if you are not a bird you cannot be an owl.
Not B - > Not O
Hope this is helpful! Please let us know if you have any further questions.
