LSAT Explanation PT 20, S4, Q7: For every 50 dogs that contract

LSAT Question Stem

Which one of the following would it be most helpful to know in order to evaluate the argument? 

Logical Reasoning Question Type

This is an Evaluate question. 

Correct Answer

The correct answer to this question is E. 

LSAT Question Complete Explanation

Let's first analyze the argument in the passage and determine its structure. The passage presents the following argument:

Premise 1: For every 50 dogs that contract a certain disease, one will die from it.

Premise 2: A vaccine exists that is virtually 100 percent effective in preventing this disease.

Premise 3: The risk of death from complications of vaccination is one death per 5,000 vaccinations.

Conclusion: It is therefore safer for a dog to receive the vaccine than not to receive it.

Now, let's consider an "Evaluate" question for this argument: "What is the likelihood that an unvaccinated dog will contract the disease in question?" This question is crucial because it helps us determine whether the argument is valid or not.

The question type of this problem is Evaluate, which means we need to identify the most helpful piece of information to know in order to evaluate the argument.

Let's discuss each answer choice in detail:

a) The total number of dogs that die each year from all causes taken together.

This information is not directly related to the difference between receiving the vaccine or not receiving it. It doesn't help us determine if the vaccine is safer or not.

b) Whether the vaccine is effective against the disease in household pets other than dogs.

This information is irrelevant to the argument since it is only concerned with dogs, not other household pets.

c) The number of dogs that die each year from diseases other than the disease in question.

This information, while interesting, doesn't directly address the difference between receiving the vaccine or not receiving it. It doesn't help us determine if the vaccine is safer or not for dogs.

d) The likelihood that a dog will contract another disease such as rabies.

This information is also unrelated to the argument, as it focuses on a different disease. We need to know the likelihood of contracting the disease in question to evaluate the argument.

e) The likelihood that an unvaccinated dog will contract the disease in question.

This is the correct answer because it directly addresses the missing information needed to evaluate the argument. If we know the likelihood of an unvaccinated dog contracting the disease, we can determine if it's safer for a dog to receive the vaccine or not. For example, if the likelihood is very low, it might not be safer for a dog to get the vaccine. On the other hand, if the likelihood is high, the vaccine would be a safer option.

In conclusion, the most helpful piece of information to know in order to evaluate the argument is the likelihood that an unvaccinated dog will contract the disease in question, making answer choice E the correct one.