#20 - Geologist: A new method for forecasting earthquakes

[Administrator]

Complete Question Explanation

Justify. The correct answer choice is (B).

Answer choice (A):

Answer choice (B): This is the correct answer choice.

Answer choice (C):

Answer choice (D):

Answer choice (E):

[mN2mmvf]

Hi,

I'm trying to understand the difference between choices (B) and (E) for this question.

Choice (E) says the method won't be useful if its predictions never distinguish between big and small earthquakes.
Choice (B) says the method won't be useful *unless* its predictions always distinguish between big and small earthquakes.

What's the difference, exactly?

Thanks!

[Francis O'Rourke]

The Geologist's conclusion was that the new method is unlikely to be useful

I would summarize the evidence presented as follows:

• The new method gives a 2.5 point range
• this range can be the difference between a marginally perceptible shaking and a damaging quake.

What you should see is uncertainty contained in the phrase "can be." It may be that the range fails to distinguish between minor and severe events 1% of the time, 50% of the time, or 100% of the time. We don't have enough information to know how frequently this method fails as a predictor.

Answer choice (E) only applies to techniques that never distinguish between small and catastrophic events. Since the stimulus only says that the new method can fail to distinguish, the information in answer choice (E) is useless to us for justifying the conclusion.

Answer choice (B) tells us that if a method does not always differentiate between small and substantial events, it is unlikely to be useful. That exactly connects what we learned about the new method in the stimulus (it doesn't always distinguish) to what the geologist alleges in the conclusion (it is unlikely to be useful)

[mN2mmvf]

Makes total sense. Thank you very much!!