Some researchers are going to put you to sleep.
During the two days that your sleep will last, they will briefly wake you up either once or twice, depending on the toss of a fair coin (Heads: once; Tails: twice). After each waking, they
will put you to back to sleep with a drug that makes you forget that waking.
When you are first awakened, to what degree ought you believe that the outcome of the coin toss is Heads?
When you are FIRST awakened,...
The assumption is that the narrator who is giving the information is telling the truth. The probability is then 1/2.
Some versions of the problem avoid this conclusion by different wording, so that you don't know whether it is the first time you woke up, or just the first time you remember waking up. In that case, I agree with Charlie's analysis.
Posted by broll
on 2018-01-22 20:58:50