timtyler comments on Beauty quips, "I'd shut up and multiply!" - Less Wrong

6 Post author: neq1 07 May 2010 02:34PM

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Comment author: neq1 07 May 2010 08:44:27PM 0 points [-]

There is a mismatch between the betting question and the original question about probability.

At an awakening, she has no more information about heads or tails than she had originally, but we're forcing her to bet twice under tails. So, even if her credence for heads was a half, she still wouldn't make the bet.

Suppose I am going to flip a coin and I tell you you win $1 if heads and lose $2 if tails. You could calculate that the p(H) would have to be 2/3 in order for this to be a fair bet (have 0 expectation). That doesn't imply that the p(H) is actually 2/3. It's a different question. This is a really important point, a point that I think has caused much confusion.

Comment author: timtyler 10 May 2010 06:39:56AM 0 points [-]

What do you think the word "credence" means? I am thinking that perhaps that is the cause of your problems.

Comment author: neq1 10 May 2010 02:17:48PM 0 points [-]

I'm treating credence for heads as her confidence in heads, as expressed as a number between 0 and 1 (inclusive), given everything she knows at the time. I see it as the same things as a posterior probability.

I don't think disagreement is due to different uses of the word credence. It appears to me that we are all talking about the same thing.