Just how much do you not get?

[Magpie]

Why does "If you can't tell what you did is wrong, you definitely shouldn't get the marks that you're trying to say you are close enough for." never work? I mean, I understand that they're still going to want me to explain it to them (at least, they should). But if I look at someone's diagram and think that they don't know the first thing about what they're supposed to be doing, why does that person think that the fact that they obviously did have all the information right (because their calculations where right) means that they should argue with me about it for five minutes?

(I agree, sometimes marking can be hard because you're looking for something specific. But if we ask you to draw a diagram, it doesn't mean "plunk anything down on the paper and you get full marks as long as we can't prove that it's wrong". )

[Exaspera]

Yep, that's like assigning a paper that they sort of know what to do but not really, so they stab around at a whole bunch of things hoping to dazzle you with their footwork.