PrepTest 158, Section 3, Question 1
In the previous two years, significantly more rain(24 more words not shown)
The reasoning in the argument(11 more words not shown)
- Acontains a premise(7 more words not shown)
- Bdraws an inference(18 more words not shown)
- Coveremphasizes the possibility(13 more words not shown)
- Dconcludes that two(18 more words not shown)
- Euses evidence drawn(9 more words not shown)
Reading the argument
Two years? That's a pretty small pattern to use for this year's forecast.
Maybe September really is usually wetter than July in Browning. But maybe the last two Septembers were unusually wet, or the last two Julys were unusually dry. A short stretch of unusual weather could give us these results even if the longer history looked quite different. We haven't been given that history.
What we’re looking for
The conclusion only says “probably,” so we shouldn't accuse the author of claiming a guarantee. Still, why should these two comparisons be enough to establish what will probably happen next? That's the weakness I'd look for in the answers: a forecast resting on very little past evidence.
Working the answers
- A
The premise concerns what happened in the last two years. The conclusion concerns what will happen this year. We can accept the past results without already accepting the forecast, so the premise doesn't assume the conclusion. The problem is how little evidence supports the forecast.
- BCorrect
The future event is this year's rainfall comparison. The limited past instances are the two previous September-versus-July comparisons. Two results can form an apparent pattern without giving us a reliable picture of the area's usual weather. B describes the leap we're questioning.
- C
This concern sounds familiar, but check who is raising it. We worried that unusual rainfall might distort the apparent pattern. The author doesn't emphasize that possibility at all; the argument proceeds without addressing it. We can't criticize the author for overemphasizing an objection the author never makes.
- D
What are the two phenomena, and where does the author give many instances of both occurring together? The passage gives two years of rainfall comparisons and projects that pattern into a third year. D doesn't describe that move. Don't pick a familiar-sounding flaw without matching its pieces to the actual argument.
- E
We aren't told that the rainfall figures came from a questionable source. Even perfectly accurate figures could leave us with only two years of data. We can accept the reported rainfall and still question the prediction; we don't need to challenge whoever supplied the numbers.
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