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Exactly this. I came to make the same comment, but unsurprisingly someone has beat me to it. In particular, the answer to the "paradox" in a nutshell is this:

> There's no change in belief happening, only two different beliefs. First is "1/2 of the times it is flipped, the coin will be heads". Seconds is "1/3 of the times I am awakened, the coin will be heads".



Yep it's not a paradox, it's actually just two separate questions.

1. What is the probability that the coin toss was heads (as posted in question)

    set of possibilities: { H, T }
2. What is the probability that you have awoken due to the coin coming up heads? (implied by question, but not explicitly asked)

    set of possibilities: { H, T, T }


The question is actually: "given that I have woken up, what is the probability of heads?"

This is the question that is disputed by sources in OP. Both sides are addressing the same question.




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