Logical reasoning PrepTest 107 · Section 1 · Question 10

Question prompt

The symptoms of hepatitis Remaining source text redacted.
Why the credited answer is right

Credited answer: D

The notes below walk through why it fits the stem and how to eliminate the rest.

Argument or Facts

Facts

Valid or Flawed

NA

Question Type

Paradox Questions

Stimulus Summary

Hep A takes 60+ days after infection to show symptoms. A study had 50 people receive a vaccine that is 100% effective, but some of them got hep A.

Answer Anticipation

As with all Paradox questions, we should start by clearly defining the paradox. In this question, that ends up being particularly important because it allows us to ignore information that’s likely included just to confuse us!
So what’s the paradox here? Well, the timeline for hep A developing doesn’t really create any paradox. Neither does a study where half the people receive a vaccine and half receive a placebo. Even people from both groups getting hep A wouldn’t be weird - after all, maybe the vaccine is like the flu vaccine and people can still get sick after getting it.
However, here, it’s noted that the vaccine is “completely effective” in preventing infection. So the paradox is related to the individuals in the test who received the vaccine and still showed hep A symptoms, despite it being 100% effective in preventing infection. Note that this means the placebo group is unrelated to the paradox, as there’s no paradox in some of them getting hep A since they weren’t vaccinated!
We could head to the answers looking for something that resolves the paradox, but we could also get more specific with our anticipation by considering other information to see if we can figure out a resolution. The only other info presented is that hep A takes 60+ days after infection to show symptoms. Can this explain the results of the test? It can. The vaccine prevents infection, not symptoms after infection, so the people who received the vaccine but went on to develop symptoms must have already been infected but in that 60-day window. Let’s find an answer bringing that up.

Answer choices

  1. A
    The placebo did not Remaining source text redacted.
    Why choice A is not credited
    The paradox didn’t relate to the placebo group getting hepatitis symptoms, as it would be expected that some of them would show symptoms of the disease.
  2. B
    More members of the Remaining source text redacted.
    Why choice B is not credited
    This answer about patients recognizing symptoms would only be relevant if the study relied on self-reported results, but there’s no indication that’s the case.
  3. C
    The people who received Remaining source text redacted.
    Why choice C is not credited
    The stimulus doesn’t discuss how being in good physical condition impacts hepatitis A infection rates.
  4. D
    The vaccinated people who Remaining source text redacted.
    Why choice D matches the stem
    Finally, an answer that addresses the vaccinated group! The vaccine prevents infection, so if some of the people were already infected when they received the vaccine, that would explain how they still ended up with symptoms. This answer resolves the paradox, making it correct.
  5. E
    Of the people who Remaining source text redacted.
    Why choice E is not credited
    Recovery is out of scope of a discussion of prevention.

What this tests

Question analytics

Based on historical answer selection rates for this question.

Answer choice distribution

  1. A 6%
  2. B 5%
  3. C 1%
  4. D Credited 75%
  5. E 13%

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