Story time: At a party of math students, the following dialogue happened between classmates (names changed):

Alice: "Do you know whether Carol will come to the party?"

Bob: "She will come, but somewhat later. I think she will be there in half an hour."

Alice: "I am not interested in whether she will come or not. If I wanted to know that information, I would simply have asked you whether she will come and if you did not know, you would simply have answered 'I don't know'. But this is not the question that I asked. I just wanted to know whether you have the knowledge whether she will come or not and that is why i formulated the question exactly this way and not differently."