Q7 - For every 50 dogs that contract a certain dsease

[QIAOH648]

I could not understand the answer E, since I chose C.

Thank you~

[smiller]

Apologies for our slow reply.

Here's the argument core:

Premise: 1/50 dogs who contract a disease die.
Premise: A vaccine is almost 100% effective in preventing the disease.
Premise: The risk of death from the vaccine is 1/5000.
Conclusion: It is safer for a dog to receive the vaccine than not.


It's easy to focus on the facts that we're given and not notice what we haven't been told. The first premise only tells us what happens to dogs who contract the disease. We have no idea how likely it is for a dog to contract the disease. What if any given dog has a 1/1,000,000 chance of contracting the disease? If that's true, receiving the vaccine is not safer. This is why choice (E) is correct: that information could very directly tell us whether it's safer for a dog to get the vaccine or not.

Choice (C) is tempting, but it doesn't address the difference between receiving the vaccine or not receiving it as directly as choice (E) does.