Throwing Stones at it:
“Daddy – has anybody ever measured how much anybody knew?
Oh yes. Often. But I don’t quite know what the answers meant. They do it with examinations and tests and quizzes, but it’s like trying to find out how big a piece of paper is by throwing stones at it.
How do you mean?
I mean – if you throw stones at two pieces of paper from the same distance and you find that you hit one piece more often than the other, then probably the one that you hit most will be bigger than the other. In the same way, in an examination you throw a lot of questions at the students, and if you find that you hit more pieces of knowledge in one student than in the others, then you think that student must know more. That’s the idea.”