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comment by mike
mike  ·  3142 days ago  ·  link  ·    ·  parent  ·  post: The fake coin probability problem

Yes, you flip the same coin 3 times. Your diagram is a good start, but what is the probability of heads on the next toss?





Devac  ·  3142 days ago  ·  link  ·  
This comment has been deleted.
mike  ·  3142 days ago  ·  link  ·  

Something to think about: each flip of the coin where you see heads changes the probability you've got the fake coin. If you flipped the coin 100 times and got heads every time, I think you'd be about 100% certain that the next time it will be heads.

snoodog  ·  3142 days ago  ·  link  ·  

I thought of it the same way Devac thought about it but given the hint it comes down to something like this.

Edits for formatting

Turn Fake ------- Real Probability

1 1/2 ---- 1 / (.5 +1)

1 1/4 ------- 1/(.25+1 )

1 1/8 --------- 1/(.125+1 )

1 1/16 -------- 1/(.0625+1 ) -94%

1 1/2^N ---------- 1/(.5^N+1 )