PrepTest 132, Section 4, Question 9
If a mother's first child is born before(39 more words not shown)
The questionable reasoning in the(14 more words not shown)
- AArtisans who finish(32 more words not shown)
- BAll responsible pet(21 more words not shown)
- CIf a movie(36 more words not shown)
- DIf a business(25 more words not shown)
- ETai will go(18 more words not shown)
Reading the argument
“Likely” leaves room for an exception. A mother whose first child arrived early could have a second child who did not.
The rule starts with the first birth and tells us what tends to happen with the second. The argument instead starts with the second birth not being early and draws a conclusion about the first. It hasn't shown that the probability works that way around. We'd need more information about the overall pattern of first and second births to decide how likely an early first birth is among mothers whose second birth was not early.
That uncertainty matters. If an early first birth guaranteed an early second birth, a second birth that wasn't early would rule out an early first birth. But the stated rule gives us a tendency, not that guarantee.
What we’re looking for
For the parallel, preserve the whole sequence: one event makes another likely; the second event didn't happen; therefore, the first event probably didn't happen. Keep track of which event is missing in the evidence and which event is denied in the conclusion.
Working the answers
- A
Finishing the project corresponds to an early first birth, and attending the fair corresponds to an early second birth. But A starts with Ben not finishing: the first event is absent. Our argument starts with the second event absent. To match, A would need to start with Ben not attending and infer that he probably didn't finish.
- B
Responsible pet ownership makes being good with children likely. B then starts with someone being good with children and infers responsible pet ownership. That uses the presence of the second trait to infer the first. Our argument uses the absence of the second event to infer the absence of the first.
- CCorrect
The original movie's success matches the early first birth. The sequel's success matches the early second birth. In each case, the first event makes the second likely, without guaranteeing it.
Then the sequel wasn't a hit, just as the second child wasn't early. The conclusion says the original probably wasn't a hit, just as the first child probably wasn't early. The direction, missing events, and uncertainty all match.
- D
The rule says a business likely to fail will not attract investment. Pallid Starr meets that description, and the conclusion applies the rule in the same direction. The original does something different: it starts with the later outcome missing and reasons back to the earlier event.
- E
Nice weather is required for sailing. E treats meeting that requirement as a reason to predict sailing, even though Tai might stay home for another reason. That is a different mistake. It starts with a required condition being present, not with the second event of a probable connection being absent.
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