CCC comments on Conservation of Expected Evidence - Less Wrong

68 Post author: Eliezer_Yudkowsky 13 August 2007 03:55PM

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Comment author: CCC 17 August 2016 03:19:57PM 0 points [-]

At 10am tomorrow, I can legitimately express my confidence in the proposition "the cable guy will arrive after noon" is different to what it was today.

There are two cases to consider:

  • The cable guy arrived before 10am (occurs with 25% probability). In this case, I expect that he has a close on zero probability of arriving after noon.
  • The cable guy is known not to have arrived before 10am (occurs with 75% probability). At this point, I calculate that the odds of the cable guy turning up after noon are two in three.

But none of this takes anything away from the original statement:

"There is no possible plan you can devise, no clever strategy, no cunning device, by which you can legitimately expect your confidence in a fixed proposition to be higher (on average) than before."

This is because I am changing my probability estimate on the basis of new information received - it's not a fixed proposition.