Jonathan_Graehl 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: Jonathan_Graehl 15 May 2010 12:06:04AM 0 points [-]

this is a probability tree corresponding to an arbitrary wake up day

Huh? If tails, then Beauty is (always) woken on Monday. Why do you have probability=1/2 there?

(likewise for Tuesday)

Comment author: neq1 15 May 2010 12:28:55AM 0 points [-]

The probability represents how she should see things when she wakes up.

She knows she's awake. She knows heads had probability 0.5. She knows that, if it landed heads, it's Monday with probability 1. She knows that, if it landed tails, it's either Monday or Tuesday. Since there is no way for her to distinguish between the two, she views them as equally likely. Thus, if tails, it's Monday with probability 0.5 and Tuesday with probability 0.5.

Comment author: Jonathan_Graehl 15 May 2010 05:47:59AM *  0 points [-]

Okay, I now understand what you mean by that tree.