adkikani wrote:
Hi
GMATNinja generis @GmatininjaTwo
How do we perform PoE for B and C when RESULTS or outcomes are NOT known?
Before we look at POE, let's make sure we understand the argument. The conclusion is that "it is a waste of money to order follow-up x-rays of ankle fractures initially judged stable." How does the author arrive at this conclusion?
- "Often patients with ankle fractures that are stable are given follow-up x-ray because their orthopedists are concerned about possibly having misjudged the stability of the fracture." - The orthopedists think that the fractures are stable and don't require surgery. Just in case, some time after making that initial judgment, follow-up x-rays are ordered to check the injury.
- A number of follow-up x-rays were reviewed.
- In that review, all the fractures that had initially been judged stable were found to have healed correctly.
Based on the review, it seems as though the follow-up x-rays are unnecessary. But how many x-rays were actually reviewed? We only know that "a
number" of x-rays were reviewed. What if the review only included a handful of patients with the same highly-talented orthopedist? Without knowing the extent of the review, we cannot safely make a generalization.
We are looking for something that strengthens the argument.
Quote:
B) Many ankle injuries for which an initial x-ray is ordered are revealed by the x-ray not to involve any fracture of the ankle.
Choice (B) describes the situation in which the initial x-ray reveals that the ankle is not fractured. The argument is not concerned with this situation. The argument deals with follow-up x-rays of
stable ankle fractures. Choice (B) is irrelevant and can be eliminated.
Quote:
C) X-rays of patients of many different orthopedists working in several hospitals were reviewed.
Ah ha... choice (C) tells us something about the extent of the review.
Does this prove that the conclusion is valid? Not at all. We still don't know the exact extent of the study. But does (C)
strengthen the argument? Absolutely. Without choice (C), it would be entirely possible, for example, that the review included only one orthopedist or only one hospital. With (C), we at least know that the review included many different orthopedists and hospitals.
Choice (C) makes the argument
better. Even though it does not prove that the conclusion is true, it certainly strengthens the argument. Thus, (C) is the best answer.
I hope that helps!
Can you please help me understand what this means "Many ankle injuries for which an initial x-ray is ordered are revealed by the x-ray not to involve any fracture of the ankle"
What do we mean by "not to involve any fracture of the ankle" in the above? I think I am having problem in comprehending this.