I think the answer is A. Please find below my 2 cents

The conclusion of Pediatricians is that pet birds are more likely to bite young children below age 13 than bite older people. The evidence for that is a study which should ring alarm for representativeness of the issues. The study indicates that "majority of all bird bites requiring medical attention involved children under 13". But not all all bird bites necessarily require medical attention and option A says the same that birds are just as likely; if not more likely to bite people of age over 13 as to bite younger children.

A team of pediatricians recently announced that pet birds are more likely to bite children under age 13 than people of any other age group. The team's finding was based on a study showing that the majority of all bird bites requiring medical attention involved children under 13. The study also found that the birds most likely to bite are cockatiels and parakeets.

The team's finding was based on a study showing that the majority of all bird bites requiring medical attention involved children under 13.
- In the majority of cases medical attention was needed for children under 13, and therefore such cases got recorded in to study database
- it may be possible that people older than 13 got bitten more often than children under 13, but such cases did not get recorded because they did not need medical attention

Which of the following, if true, would most weaken the pediatricians' conclusion that birds are more likely to bite children under age 13 than people of any other age group?

A. More than half of bird bites not requiring medical attention, which exceed the number requiring such attention, involve people aged 13 and older.
- Study did not consider such cases. Therefore it is weakening the conclusion
-CORRECT

B. The majority of bird bites resulting in the death of the bitten person involve people aged 65 and older.
- Argument has nothing to do with death, Out of scope

C. Many serious bird bites affecting children under age 13 are inflicted by birds other than cockatiels and parakeets.
- Conclusion is not specific to cockatiels or parakeets. - Irrelevant

D. Most bird bites in children under age 13 that require medical attention are far less serious than they initially appear.
- Out of scope. Not comparing the seriousness of birds bite

E. Most parents can learn to treat bird bites effectively if they avail themselves of a small amount of medical information.
- Irrelevant

Pediatricians concluded based on a study showing that the majority of all bird bites requiring medical attention involved children under 13.

Pre-thinking - if birds bites don't require medical attention and people suffered are >13 years old, then it will weak Pediatricians' conclusion.

Which of the following, if true, would most weaken the pediatricians' conclusion that birds are more likely to bite children under age 13 than people of any other age group?

A. More than half of bird bites not requiring medical attention, which exceed the number requiring such attention, involve people aged 13 and older. -> It is in-lined with our pre-thinking. Let's keep it.

B. The majority of bird bites resulting in the death of the bitten person involve people aged 65 and older. -> we want to know, if medical attention was required for >13 years old or not. Incorrect.

C. Many serious bird bites affecting children under age 13 are inflicted by birds other than cockatiels and parakeets. -> Incorrect, we need to get data for medical attention required or not for >13 years.

D. Most bird bites in children under age 13 that require medical attention are far less serious than they initially appear. -> We don't know about medical attention. Incorrect.

E. Most parents can learn to treat bird bites effectively if they avail themselves of a small amount of medical information. -> Irrelevant.

So, I think A.

Official Explanation:

A

Step 1: Identify the Question Type

This stem contains a wealth of helpful information. Not only do we see the telltale keyword “weaken” indicating the question type, but we also have the conclusion of the argument stated directly in the stem. Part of our job is already done.

Step 2: Untangle the Stimulus

The basic conclusion of the pediatricians is that pet birds are more likely to bite young children than older people. The evidence for this is a study, which should ring alarm bells for representativeness issues. The study indicates that when we look at injuries that required medical attention, we see that most of the injuries were to young children.

Step 3: Predict the Answer

But not all bird bites necessarily require medical attention, so in order for this study’s results to prove that birds are more likely to bite young children overall, we need proof that the bird bites requiring medical attention are representative of all bird bites. So to weaken this argument, let’s find a choice that essentially says, “Bites that require medical attention are not representative of bites in general.”

Step 4: Evaluate the Choices

You’ll then be drawn to choice (A): Looking at all bird bite injuries reveals that most of them don’t require medical attention, and of those that don’t, more than half of them are suffered by people over the age of 13. (A) would actually indicate that birds are just as likely, if not more likely, to bite people over the age of 13 as to bite younger children. Thus, choice (A) is the correct answer. Just because senior citizens are more likely to die from bird bites, as (B) says, doesn’t mean that they’re more likely to be bitten in the first place. (C) improperly seizes on the last sentence of the argument, which is a tangential statement that has no bearing on the overall conclusion. (D) is off base because the argument deals with the likelihood that a bird will bite someone, not with the likelihood that the bite is serious. (E) commits a similar error by dealing with treatment; this argument is only concerned with the relative frequency of bird bites occurring in the first place and not with the treatment plans for bites that have already occurred. Choice (A) is correct.
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