

ipe Regular user 174 Posts 
If you choose an answer to this question at random, what is the probability that you will be correct?
A) 25% B) 50% C) 0% D) 25%
What would a real mindreader do?

landmark Inner circle within a triangle 4673 Posts 
"this question " is illdefined.
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All proceeds to nonprofit charity Open Heart Magic. You can read my daily blog at Musings, Memories, and Magic 
Scott Cram Inner circle 2676 Posts 
The choices defat each other in a nontransitive cycle (think rock/paper/scissors, where none of the choices are always the best), so none of the answers can be chosen at random with the correct probability.

landmark Inner circle within a triangle 4673 Posts 
Imagine this were not a multiple choice question. Rather than asking the probability of answering the question, ask what is the correct answer.
If it is answerable then there is some probability >0 of being correct if answering at random; if not answerable, then the P=0. There is no way to distinguish between the two cases.
Gerald Deutsch's Perverse Magic: The First Sixteen Years available now.
All proceeds to nonprofit charity Open Heart Magic. You can read my daily blog at Musings, Memories, and Magic 
ipe Regular user 174 Posts 
Quote:
On Nov 3, 2018, landmark wrote: What if the options would be: A) 25% B) 50% C) This question is illdefined D) 25%
What would a real mindreader do?

ipe Regular user 174 Posts 
Quote:
On Nov 3, 2018, Scott Cram wrote: If you cannot choose the correct answer, so 0% is the correct answer; but you can choose "0%" from the multiple options available.
What would a real mindreader do?

landmark Inner circle within a triangle 4673 Posts 
Choice C (illdefined) case is not an answer; it is a statement about the nature of the question.It could just as well be replaced by "I like this question."
Gerald Deutsch's Perverse Magic: The First Sixteen Years available now.
All proceeds to nonprofit charity Open Heart Magic. You can read my daily blog at Musings, Memories, and Magic 
ipe Regular user 174 Posts 
Landmark, I agree with you, I was just in the role of puzzleproposer.
What would a real mindreader do?

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