PrepTest 152, Section 2, Question 16
Most pet owners who take allergy medication are(26 more words not shown)
Which one of the following(15 more words not shown)
- AMost cars taken(26 more words not shown)
- BMost cars taken(23 more words not shown)
- CMost cars that(31 more words not shown)
- DMost cars taken(28 more words not shown)
- EMost cars taken(28 more words not shown)
Reading the argument
Those are two different groups. We started with pet owners who take allergy medication. Most of those people are allergic to pets. Now we're talking about Chuck, who might become allergic to his dog, and predicting that he'll take medication. We haven't learned what most allergic pet owners do.
Maybe many of them put up with the symptoms or avoid their pets instead. The people who choose medication could be a small fraction of all allergic pet owners. Even if nearly everyone in that small medication-taking group has a pet allergy, that doesn't make medication the likely choice for someone who develops that allergy. And the premise leaves room for a few pet owners who take the medication for something else, such as pollen.
What we’re looking for
For the parallel flaw, look for that switch in the starting group: most people who do something have a certain problem, so someone with that problem will probably do that thing.
Working the answers
- A
This keeps the same starting group. Most cars taken to Acme have electrical problems, and Anastasia's car has been taken to Acme. That gives us a reason to think her car probably has an electrical problem. It doesn't guarantee that her car is typical, but the argument stays within the group described by its evidence. Chuck's argument doesn't.
- BCorrect
Being taken to Acme plays the role of taking allergy medication; having an electrical problem plays the role of having a pet allergy. The premise describes cars taken to Acme. The conclusion instead starts with a car that has an electrical problem and predicts that it will be taken there. Plenty of cars with electrical problems might go to other shops, just as plenty of allergic pet owners might skip medication. Same group switch, same unsupported prediction.
- C
This starts with cars taken to Acme that mostly do not have electrical problems, then predicts that a car with an electrical problem will probably not go there. It moves from a pattern among Acme's customers to a prediction about who will stay away. Our argument instead moves from medication users mostly having an allergy to an allergic person probably using medication.
- D
This uses the same premise as B, but it predicts what happens to a car without electrical problems: it probably won't go to Acme. Chuck's argument predicts what someone with an allergy will do. It doesn't predict that someone without an allergy will probably avoid medication.
- E
This adds a belief that the original argument never uses. Anastasia merely thinks her car has an electrical problem. Chuck's conclusion is about what he will probably do if he actually develops an allergy, not if he thinks he has one. B matches that actual-condition starting point exactly.
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