I am marking an exam for a course I tutor. One student has given two answers for a particular question in the exam – one answer is fully correct, while the other is completely wrong.
Each answer has full working and explanation of how the answers were derived. It appears that the student wasn't sure which method they should use, and so hedged their bets by attempting both and hoping one of them was right. (The student presented their answer as "it is either X or Y", and in later questions gave parallel answers depending on whether X or Y was correct - I don't believe it was reworking that they forgot to cross out.)
How should I mark this question?
- Full marks since they produced a right answer?
- Partial marks because they are "half-right"?
- Or no marks because they haven't demonstrated full understanding of the problem?