If you assume that the guard’s probability of making this statement (and only this statement) is the same in all circumstances where the statement is true, then the answer is 1⁄3. Otherwise, it depends on what you know about the psychology of the guard.
If you assume that the guard’s probability of making this statement (and only this statement) is the same in all circumstances where the statement is true, then the answer is 1⁄3. Otherwise, it depends on what you know about the psychology of the guard.