PrepTest 103, Section 2, Question 11
Commercial passenger airplanes can be equipped with a(56 more words not shown)
Which one of the following,(6 more words not shown)
- AEvasive action taken(12 more words not shown)
- BCommercial passenger airplanes(19 more words not shown)
- CCommercial passenger airplanes(8 more words not shown)
- DA study by(16 more words not shown)
- EThe collision-avoidance radar(20 more words not shown)
Reading the argument
What if dodging a plane that is not there hurts someone?
The system warns pilots about possible collisions, which sounds useful. But it also frequently detects phantom airplanes. Imagine a sudden maneuver throwing passengers against their seats or causing someone to hit their head. That is a possible cost of responding to a false alarm, even though no collision was waiting to happen.
We therefore need to compare the danger the system prevents with any danger its use creates. It might still make passengers safer overall. The fact that it warns pilots, however, does not settle that comparison by itself.
What we’re looking for
For a strengthener, I would like to learn that these evasive maneuvers do not injure passengers. Evidence of a large reduction in actual collisions could also help. Either route would support the claim that the system improves safety despite its false alarms.
Working the answers
- ACorrect
If evasive action in response to the warnings poses no risk to passengers, the specific cost we worried about is removed. The pilot's reaction to a phantom plane would not expose passengers to the injury risk in our example.
That makes the false alarms less of an objection to the system's safety benefit. A does not need to prove that every possible concern about the equipment has been resolved. It strengthens the argument by directly answering this important concern.
- B
Knowing that collisions are more likely on the ground than in the air does not tell us whether the system makes passengers safer. Both risks could exist, and we still need to compare equipped airplanes with comparable unequipped airplanes. Ranking where collisions are more likely is not that comparison.
- C
Rare collisions could reflect effective prevention, or they could be rare for other reasons. This does not tell us whether the radar system contributes to that result or whether responding to its false alarms adds a competing risk. A low overall collision rate does not establish the system's net effect.
- D
A 63 percent invalid-warning rate does not show that the remaining 37 percent prevented collisions. A valid warning of a possible collision is not proof that an accident would otherwise have happened.
We also still do not know the effects of reacting to all those invalid warnings. D gives a more precise frequency for a problem the passage already mentions, without establishing the safety comparison. A directly removes the risk raised by that problem.
- E
This describes how the equipment operates. Scanning the sky and calculating distances could be part of a helpful system, but that description alone does not tell us how accurately it works or what risks its warnings create. We need evidence about passenger safety, not merely a description of the device.
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