Writing multiple-choice questions that do not leak the answer
Most hand-written MCQs can be answered without knowing the subject. The tells that give the answer away, and how to write options that do not.
27 August 2026 2 min read
A multiple-choice question is supposed to measure whether a student knows something. A surprising share of them measure whether a student is good at multiple-choice questions, which is a real skill, but not the one you are grading.
The four tells
- The longest option is correct. This is the most common leak by a wide margin. Correct answers get qualified with "because", "only when", "except in", while distractors are written quickly. Students notice this pattern long before teachers do.
- Grammar agreement. The stem ends in "an" and only one option starts with a vowel. Or the stem is plural and three options are singular. The subject is not being tested here.
- Absolutes. Options containing "always" or "never" are almost always wrong, and every experienced student knows to eliminate them first.
- The absurd distractor. An option nobody would pick reduces a four-option question to a three-option one, and two of those are usually eliminable. What looked like a 25% guess is a 50% guess.
Write the distractors from real errors
The best source of wrong options is your own marking. Every distractor should be an answer a real student actually produced: a sign error, a unit conversion missed, a formula applied one step too early. Distractors invented at the desk tend to be either obviously wrong or accidentally defensible; distractors harvested from student work are neither.
This also turns the question into a diagnostic. When you see which wrong option the group clustered on, you learn what to reteach.
Two structural rules
Keep every option roughly the same length, and put the shared wording in the stem rather than repeating it in all four options. If three options begin "the process by which", that phrase belongs in the question.
And vary the position of the correct answer deliberately. Hand-written papers cluster correct answers at B and C, because A feels too early and D feels like giving up. Over a twenty-question paper, that is exploitable.
The check that takes two minutes
Cover the stem and read only the four options. If you can still guess which is correct, the question leaks, and a student who did not study will guess it too.
Sources
Frequently asked questions
How can I tell if my MCQ leaks the answer?
Cover the question stem and read only the options. If the correct one is still guessable, because it is longest, most qualified, or the only grammatically fitting one, the question can be answered without knowing the subject.
Where should wrong options come from?
From errors real students have made in your marking: a sign error, a missed unit conversion, a formula applied too early. Invented distractors are either obviously wrong or accidentally defensible.
How many options should a question have?
Four is conventional, but three plausible options beat four where the fourth is absurd. An option nobody picks does not lower the guessing rate, it only makes the paper longer.
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