I had a bit of a different situation during my Uni education than any mentioned here... I'm not sure if it is the best solution to evaluating the students, but it is definitely implemented and has been used for several generations (in Croatia, Computer Science).
The utterly strange this is, we had multiple choice exams for mathematical problems and in general, other types of subjects that require you to solve exercises, tasks or problems and get a number as an answer.
The main points of how it worked:
- for each question, you had N different answers (where N would be the same for the whole exam). (N ~ 4 or 5, typically)
the answers offered were usually:
- 1 correct answer
- 1 correct answer * 10^x (e.g. if the right answer was 23.5 you might have 2.35 offered)
2 answers you could get by making a low-level calculus mistake in the typical solution-process (1 direct and 1 with a *10^x shift, as with the correct answer)
(e.g. if there's a standardized procedure for solving the problem, it is the answer you would get if you flip a sign somewhere by accident)
- 1 completely wrong answer
- the marks were distributed as:
- +1 for the correct answer
- 0 for unanswered
- a bit more than -1/N for wrong answer (e.g. if N = 5, then the wrong answer might be -0.25 instead of -0.20)
additionally, for the correct answer to be accepted, you had to enclose a paper with your full solution to that question (where you did your calculations).
They weren't checking this very diligently for every answer, but you were always aware that they could.
This tried to encourage the educated guesses (as you have your calculations, and maybe you're unsure between two answers because you're unsure if you used the right procedure). On the other hand, the penalty also discouraged complete guesses, as the potential negative marks were higher than the potential gain.
Of course, such a system still has plenty shortcomings. A typical problem situation was the student would having the right solution in his calculation, but transferred the wrong answer to the multiple choice answer sheet. The policies varied with different courses, although commonly, such an answer was not accepted, to prevent students for purposefully offering two answers and having a better chance of scoring.
I just realized I haven't actually offered my direct answer to the question. Here it goes:
In the system I describe, I would say it is unethical to try and guess in multiple choice exams. But, unlike all the other multiple choice setups, the one described here has a way to verify weather you guessed or not (if you have not submitted the full procedure for your answer, you must have guessed) and because of that, it stops depending solely on the students "honor"