PrepTest 107, Section 1, Question 7
In Debbie's magic act, a volunteer supposedly selects(103 more words not shown)
Which one of the following(9 more words not shown)
- AThe skeptic failed(17 more words not shown)
- BThe skeptic failed(18 more words not shown)
- CThe skeptic failed(19 more words not shown)
- DThe skeptic failed(24 more words not shown)
- EThe skeptic failed(17 more words not shown)
Reading the argument
Not finding sleight of hand doesn't necessarily mean Debbie didn't use it. That's my first concern when the skeptic reviews the video. What if Debbie is simply good enough that the trick isn't detected? The performance is described cautiously throughout: the card is supposedly chosen randomly, and Debbie supposedly reveals that same card. We shouldn't treat an apparently successful demonstration as a complete explanation of how it worked.
The skeptic does try three checks. One trial looks for sleight of hand on video. Another uses the skeptic's ordinary deck. In the third, the skeptic personally chooses the card. Those are sensible ways to investigate different possible tricks. But how much does each test actually rule out?
What we’re looking for
The conclusion says Debbie uses none of the three methods. For the flaw question, my first expectation is a choice pointing out that a trick could escape detection. We still need to read the choices carefully: another gap in these tests could also show why the conclusion goes too far.
Working the answers
- ACorrect
Debbie could change methods from one trial to the next. This is a different objection from our initial concern about missing a trick on video, and it works even if the video reliably rules out sleight of hand in the first trial.
In that first trial, Debbie could use a trick deck. When the skeptic supplies an ordinary deck in the second trial, she could use sleight of hand instead. When the skeptic chooses the card in the third trial, she could again use a method that doesn't require a planted volunteer. Removing one possible method at a time doesn't establish that she never uses any of them. We'd need to account for the possibility that she has several ways to produce the same effect.
- B
Another way to detect sleight of hand doesn't show a failure in this investigation. Our initial concern was that videotaping might miss something. B doesn't say the video missed a trick or that another method would reveal one; it merely says other means of detection are possible.
- C
Requiring both methods is different from switching between methods. If Debbie needed a trick deck every time, providing a standard deck would remove something essential to her success. Her apparent success in that trial doesn't fit that explanation. The useful objection is that she can use an available alternative, not that she always needs both.
- D
The skeptic's conclusion already leaves room for some other method. Saying Debbie uses none of these three tricks is compatible with saying she uses a fourth. That possibility doesn't expose the gap in ruling out the three named methods.
- E
The skeptic never concludes that Debbie merely got lucky. The conclusion concerns which methods she uses, and it can allow a repeatable method other than those listed. Failing to discuss coincidence doesn't identify why the three tests fail to rule out the named tricks.
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