LSAT 107 | Section 1 | Logical Reasoning: Q7

LR Question 7 Explanation

QUESTION TEXT: In Debbie’s magic act, a volunteer supposedly selects a…

QUESTION TYPE: Flawed Reasoning

CONCLUSION: The skeptic concluded that Debbie used none of the three methods he tested.

REASONING: The skeptic tested each method individually and didn’t catch Debbie using them.

ANALYSIS: Did you ever play a game as a kid where someone had to guess which hand you were holding a ball in? You would keep both hands behind your back. You could trick the other kids by switching the ball depending on which hand they picked.

(I was never mean enough to try this, of course!)

That could be what Debbie did. If the skeptic was videotaping her for slight of hand she could have used a trick deck. If the skeptic gave her the deck then Debbie could have used sleight of hand.

The skeptic should have tested everything at once.

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1. CORRECT. Debbie could be very clever and switch her methods depending on what the skeptic was testing for. 
2. I’m sure there are many methods to catch sleight of hand. But as long as videotaping works well then it doesn’t matter how many others there are.
3. The skeptic would have caught Debbie if this had been the case. When he tested for the trick deck Debbie still succeeded. So she can’t have needed sleight of hand and a trick deck.
4. The skeptic didn’t say Debbie must be a magician. He just said she didn’t use one of the three techniques he tested. There could be other techniques.
5. The skeptic didn’t reach a conclusion about whether Debbie really used magic or if she had a method. He just concluded she never used the three techniques he tested.