Both answers are valid because the question is ambiguous. Asking &quot;what is your belief&quot; doesn&#x27;t work because there are multiple ways to interpret that. You can clarify such situations by putting them in a game. Probabilities are about how much you would bet on it.<p>Game 1: You get $10 every time you guess correctly. Best strategy: Guess tails because if it&#x27;s correct you get $20. If you guess heads correct you get only $10. If you got $3 for guessing tails correctly and $6 for guessing heads correctly then it would not matter what strategy you used.<p>Game 2: If you guess correctly then you get $10 by the end of the experiment. Best strategy: it doesn&#x27;t matter what you guess, if you guess tails correctly you get the $10, and if you guess heads correctly you also get $10.<p>Thirders think the question is like game 1: every time they guess correctly they win correctness points. Halfers think the question is like game 2: they either guess correctly or they don&#x27;t; you don&#x27;t get additional correctness points by guessing right twice.