PrepTest 146, Section 3, Question 5
Resident: Data indicates that 30 percent of the(37 more words not shown)
The reasoning in the resident's(11 more words not shown)
- Athe town has(6 more words not shown)
- Binadequate site drainage(5 more words not shown)
- Cstructural defects are(8 more words not shown)
- Dmany houses in(15 more words not shown)
- Esome of the(15 more words not shown)
Reading the argument
Are those the same houses?
Thirty percent have drainage problems, and 30 percent have structural defects. If every house with one problem also has the other, we've identified problems in only 30 percent of the houses. Imagine a town with 10 houses: the same 3 have both defects. Counting those 3 twice doesn't give us 6 different houses.
What we’re looking for
Even partial overlap would make the combined group smaller than 60 percent. We might also ask whether each defect threatens a house's integrity, but the arithmetic problem is already clear. For the flaw question, look for the possibility that the two groups share some houses.
Working the answers
- A
The number of houses doesn't fix the overlap problem. We can make the mistake with 10 houses or 10,000 houses. The important question is whether the two percentages count any of the same houses, not whether the town is large.
- B
This fits the resident's reasoning rather than challenging it. The resident is counting drainage problems as threats to the houses' integrity, so saying drainage can make a house unsafe supports that part of the argument. It doesn't address the unsupported addition of the two groups.
- C
Ease of repair doesn't tell us how many houses have problems. A defect could be cheap and easy to fix while still threatening the house before it is repaired. The resident is diagnosing how widespread the problems are, not deciding which repair should happen first.
- D
Many houses could lack both listed defects without contradicting the resident's claimed 60 percent. Even if the groups don't overlap, 40 percent would have neither. If they overlap completely, 70 percent would have neither. D doesn't identify the overlap that makes simply adding the percentages unreliable. Also, lacking these two defects doesn't establish that a house has no other problem.
- ECorrect
Some houses belong to both groups. Adding 30 percent and 30 percent then counts those houses twice. The two listed defects would occur in fewer than 60 percent of the houses, so those figures don't establish the resident's claimed minimum. Other problems might exist, but the argument has supplied no evidence that they make up the difference.
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