Say I have a question with answers

A (correct)
B (correct)
C (wrong)
D (wrong)

And the student answers: A,B,C.

Lets say, I add +1 point for every correct answer.
How much should I subtract for the wrong answer C? -1 point?
Or alternatively I should add +0.5 points for correct and subtract -0.25 for wrong?

  • 2
    This largely comes down to what you hope to achieve with the grading, e.g. encourage answering/discourage guessing. A related format with the same 50%-50% ratio is yes-no questions, see How to choose a good grading curve for yes/no exams?
    – Anyon
    Commented Apr 1 at 12:42
  • 4
    Somehow, writing down all of ABCD to all questions should not result in a positive grade. But I would rethink your questions and why you want them to have multiple correct answers.
    – Jon Custer
    Commented Apr 1 at 14:46
  • If you usually give 1 for a correct answer and 0 for a wrong answer, then in this case you should do the same. So A,B,C should get 3 points (because the student was correct about A, B, and D).
    – toby544
    Commented Apr 1 at 21:59
  • 2
    To build upon @Anyon's comment. do you want to grade students on content or their ability to take multiple choice tests while applying game theory to their answering and guessing approach? Commented Apr 2 at 16:49
  • 3
    You seem to be asking four independent yes–no questions, in which case you should grade them as four independent yes–no questions. Whether that means subtracting points for incorrect answers or (probably the more common option) simply counting them as worth zero points is up to you. That these questions are listed in an "ABCD" format is irrelevant to the substance of what you are doing. Commented Apr 2 at 17:58

2 Answers 2


I've seen similar style questions (years ago) on the general GRE. Four statements are made about the question/problem but the student gives one answer. That simplifies grading. Dave L Renfro kindly informed me that these are called K-type questions. There are also SATA questions--Select All That Apply.

The four answers could be:

A: Statements 2 and 3 are correct.
B: Statements 1, 2, and 4 are correct. 

I've also seen questions where there is only one correct answer but at least one other answer is almost correct.


I'll assume that a single such question isn't a major part of a student's evaluation/grade. In that case it really doesn't matter as it has only a marginal effect.

I'll suggest, pretty strongly, however, that you advertise the scheme, whatever it is prior to such questions being asked.

If you really need to finesse it, then how much a wrong answer should be penalized depends on how essential to understanding such a mistake could be.

It should make sense. It should be clear to students.

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