Logical reasoning PrepTest 106 · Section 2 · Question 7
Question prompt
For every 50 dogs
Remaining source text redacted.
Why the credited answer is right
Credited answer: E
The notes below walk through why it fits the stem and how to eliminate the rest.
Argument or Facts
Argument
Valid or Flawed
Flawed
Question Type
Argument Evaluation Questions
Stimulus Summary
1/50 dogs die from a disease. A nearly 100% effective vaccine kills 1/5000 dogs who are given it. Thus, the vaccine is safer than not getting it.
Answer Anticipation
When a conclusion includes a common type of logic, we should focus on digging into that logic. Here the conclusion is that vaccinating a dog is “safer” than not vaccinating it - a comparative conclusion. So let’s see if we get comparative premises that back this up. What do we learn about vaccinating vs. not vaccinating? We know that 1/50 dogs who get a disease (i.e., aren’t vaccinated) die from that disease, whereas 1/5000 dogs die from complications from the disease. 1/50 is a lot more than 1/5000, so the vaccine is safer, right? Wrong. If we vaccinate all dogs, then 1/5000 will die from complications from the vaccine. If we don’t vaccinate all dogs, then it’s not necessarily the case that 1/50 will die - just 1/50 that contract a certain disease. Without knowing what percentage of unvaccinated dogs end up getting the disease, we don’t know how many dogs will die compared to getting the vaccine. As such, it’d be helpful to know what percent of dogs are expected to contract the disease in order to evaluate this argument.
Answer choices
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Athe total number of Remaining source text redacted.
Why choice A is not credited
The total death rate of all dogs for all reasons doesn’t let us dig in and compare two specific causes of death. -
Bwhether the vaccine is Remaining source text redacted.
Why choice B is not credited
The conclusion is that it’s safer to vaccine “a dog” than not to vaccinate that dog, so other pets are out of scope. -
Cthe number of dogs Remaining source text redacted.
Why choice C is not credited
The vaccine is, as far as we know, for only this disease, so other diseases are out of scope. -
Dthe likelihood that a Remaining source text redacted.
Why choice D is not credited
Similar to (C), other diseases don’t change the math for comparing this disease vs. the vaccine for it. -
Ethe likelihood that an Remaining source text redacted.
Why choice E matches the stem
This answer matches our anticipation. If most unvaccinated dogs get the disease, then the vaccine will prevent deaths. If only 1/10,000 dogs get the disease, and only 1/50 of them die, then it’s safer not to risk the 1/5000 chance of complications from the vaccine. This information would help us weigh the risks of the vaccine, so it’s the correct answer.
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