Negative Marking: When It Makes Sense and When It Just Creates Anxiety
Negative marking exists to discourage guessing, but its side effect is that it penalizes the cautious candidate more than the uninformed one.
On a four-option multiple-choice exam, someone who knows nothing scores 25% by guessing. Negative marking exists to cancel out exactly that luck.
The simple math
On a four-option question, for the expected value of a completely blind guess to be zero, each wrong answer has to deduct one third of the credit for a correct answer.
The calculation: with probability 1/4 you guess right (+1 point) and with probability 3/4 you guess wrong (−1/3 point). Total: 1/4 − 3/4 × 1/3 = 0.
In Iranian exams this is usually phrased as "three wrong answers cancel one right answer," which is the same rule.
The problem that gets less attention
Negative marking cancels blind guessing, but it also penalizes informed guessing. A candidate who has definitively ruled out two options and is torn between the remaining two has a 50% chance, and guessing is the rational move. But the cautious candidate — who usually knows more, too — leaves it blank out of fear of the penalty and loses points.
The research finding: negative marking systematically favors risk-takers and hurts cautious people — and risk appetite has nothing to do with subject knowledge.
When to use negative marking
- Competitive exams with limited seats, where rank matters more than the absolute score.
- When there are many questions and little time — that is, when speed of recognition is part of what's being measured.
When not to
- Placement or diagnostic tests, where you want to know what the person knows.
- Internal organizational tests that measure training outcomes.
- When the number of questions is small (under 20) — a single mistake has a disproportionate effect.
A better alternative for most cases
Instead of negative marking, increase the number of options. On a five-option question the chance of guessing right is 20%, and on a six-option question it's 17%. That alone solves a large part of the problem without adding anxiety.
Or use short-answer questions, which can't be guessed at all.
Whatever you choose, say it clearly
The scoring rule has to be stated before the exam starts, on the first page. A candidate who doesn't know there is negative marking picks the wrong strategy, and their score won't reflect their knowledge.