PrepTest 142, Section 2, Question 23
Every brick house on River Street has a(29 more words not shown)
Which one of the following(16 more words not shown)
- ABy that line(24 more words not shown)
- BBy that line(29 more words not shown)
- CBy that line(28 more words not shown)
- DBy that line(28 more words not shown)
- EBy that line(28 more words not shown)
Reading the argument
The brick houses could be the exceptions.
Every brick house has a front yard, but not every front-yard house has to be brick. Some could be wood or concrete. So the statement about most houses with front yards concerns a larger group that might contain very few brick houses.
Imagine 1,000 houses with front yards on River Street. Only one is brick, and it has one story. The other 999 have two stories. Every brick house has a front yard, and most front-yard houses have two stories. Yet none of the brick houses has two stories. Both premises are true while the conclusion is false.
What we’re looking for
For the parallel flaw, keep those roles straight: a smaller group sits entirely inside a larger group; most of the larger group has a feature; the argument incorrectly gives that feature to most of the smaller group. It hasn't shown that the smaller group resembles the larger group in that respect.
Working the answers
- A
This moves from a smaller group to a larger one. Legislators are a subset of politicians, and most legislators have run for office; the conclusion assigns that feature to most politicians. Our original moves the other way, from most front-yard houses to most brick houses. A makes an unsupported generalization, but it reverses the direction of the transfer.
- B
We get two statements about majorities: most legislators have run, and most politicians who have run are public servants. We never get the original's all-members relationship placing one group wholly inside another. The conclusion then goes from public servants back to legislators. These overlapping groups don't form the same smaller-group, larger-group, shared-feature structure.
- C
This starts with legislators inside public servants and tells us some public servants aren't legislators. It then concludes something about who has run for office, even though neither premise mentions that feature. It also concludes “not every” rather than transferring a majority's feature to a subgroup. That is a different gap.
- DCorrect
Legislators correspond to the brick houses. Public servants correspond to all the houses with front yards. Never having run for office corresponds to having two stories.
All legislators are public servants, just as all brick houses have front yards. Most public servants have never run for office, just as most front-yard houses have two stories. Then the argument wrongly says most legislators have never run. The legislators could fall entirely within the minority of public servants who have run, just as the brick houses could fall within the minority of front-yard houses with one story.
- E
This compares two majorities with contrasting features, then concludes that most members of one group are outside the other group. It never establishes that all legislators are public servants, the counterpart of all brick houses having front yards. In fact, legislators could all be public servants while making up a small part of that group. E's attempted separation of groups isn't the original's transfer of a majority's feature to a subgroup.
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