PrepTest 137, Section 4, Question 25
Advertisement: The dental profession knows that brushing with(34 more words not shown)
The flawed reasoning in which(14 more words not shown)
- AThe nation's voters(28 more words not shown)
- BSome of the(40 more words not shown)
- CThe nation's voters(46 more words not shown)
- DThe nation's voters(36 more words not shown)
- EWe know that(27 more words not shown)
Reading the argument
Five dentists don't speak for the entire profession.
The advertisement starts with what the dental profession supposedly knows, then tells us that five dentists endorsed Blizzard's formula. How were those five selected? Would other dentists agree? Even unanimous agreement within that tiny group doesn't establish the view of dentists generally.
What we’re looking for
That's the first mistake I'd carry into this parallel-flaw question: a very small survey is used to make a broad claim about the whole group. But we should also compare exactly what the surveyed people endorsed with what the conclusion claims. Matching the sample size alone won't guarantee a match.
Working the answers
- A
The small survey does resemble our first concern: ten voters are used to speak for the nation's voters. But these voters say Gomez would be popular, and the conclusion says his policies would be best for the nation. Popularity and beneficial policies are different judgments. The dentists were asked about cavity-fighting effectiveness, which is also the subject of the conclusion. A introduces a different shift in the content of the endorsement.
- B
Ten voters can establish that some voters hold a view. That limited conclusion avoids the original leap from five dentists to the dental profession generally. There may still be a question about moving from approval of policies to approval of a candidate, but the broad population claim we're matching is missing.
- C
This uses thousands of voters instead of a tiny handful, so it doesn't reproduce the same small-sample problem. A large sample isn't automatically representative, but we aren't given a reason to treat it like the survey of five dentists. The comparison also stays among the candidates' policies rather than moving to the best way to help the nation overall.
- DCorrect
The ten voters correspond to the five dentists, and the nation's voters correspond to the whole dental profession. Both conclusions attribute a view to the entire group based on a tiny surveyed subset.
There is another matching leap worth noticing. The dentists endorse the best cavity-fighting formula available in toothpaste; the advertisement concludes that brushing with Blizzard is the best way to fight cavities. D moves from the best policies to electing Gomez as the best way to help the nation. In each case, an endorsement within one category is expanded into a claim about the best overall method.
- E
The conclusion says what 'we' know, rather than attributing knowledge to the nation's voters as a group. That misses the profession-wide claim in the advertisement. It also moves from electing Gomez being helpful to its being the best course. The dentists already endorse something as most effective within a category, so this helpful-to-best jump isn't the same comparison.
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