2026-09-02|7 min read
How to write multiple choice distractors
In short
Good distractors are collected from real student errors rather than invented: the result a student reaches after skipping a step or confusing two concepts is a ready-made distractor. Seven patterns give the answer away, among them a correct option longer than the rest, absolute qualifiers and all of the above, each letting a student reach the answer by elimination.
The difficulty of a multiple choice question comes from its options more than its stem. However well the stem is written, if three options are obviously wrong the student finds the answer without knowing the topic.
A distractor is a wrong answer that a student with a partial grasp would find plausible. Its job is not to trick anyone but to make the gap visible. What follows is where distractors come from and which patterns give the question away.
Good distractors come from real errors
Distractors are collected rather than invented. The best source is the mistakes students actually make. If you have taught a topic for a few terms you already know which step trips people up.
An example: on a subtraction question with signed numbers, some students forget to distribute the minus sign and others skip turning two negatives into a positive. The results of those two errors are two ready-made distractors. Whichever one a student marks also tells you which step they missed.
An exam written this way does more than produce a grade. It shows what to go over next lesson. If half the class marked the same distractor, that step needs teaching again.
- The result a student gets when they skip the order of operations
- The result from knowing the formula but failing the unit conversion
- The term a student picks when they confuse two neighbouring concepts
- The reading a student gives when they invert the axes of a graph
Seven patterns that give the answer away
The patterns below let a student who does not know the topic reach the answer by elimination. Look at your options once more with this in mind before the paper goes out.
- The correct option being visibly longer than the rest. Students learn to mark the most detailed one.
- Absolute qualifiers. An option carrying always, never or certainly is usually wrong, and students know it.
- Grammar that does not agree with the stem. If the stem ends in a plural, singular options rule themselves out.
- All of the above and none of the above. A student who spots two correct options goes to all of the above without knowing the topic.
- Options that contain one another. If one covers another, they cannot both be wrong, and the real number of choices drops.
- A word from the stem repeated only in the correct option. The eye catches that match.
- Numeric options listed out of order. When numbers are not sorted, the middle value starts to look like the answer.
Where the answer sits, and how many options
Correct answers should spread evenly across the letters. If most of the answers on an exam you wrote sit at C and D, that may not be chance; there is a well documented pull toward hiding the answer in the middle. Count the letters on the answer key once the paper is done.
The number of options depends on the exam format. Four is the norm in middle school exams and five in university entrance style tests. Random guessing hits 25 per cent at four options and 20 per cent at five.
Adding an option does not automatically improve the exam. Four solid options measure better than five where the last one is filler. A weak distractor is marked by nobody and adds nothing.
Checking distractors after the exam
Whether a distractor worked is only knowable afterwards. An optical reader or a hand count gives you how many students marked each option.
A distractor nobody marked is dead and quietly turns the question into a three-option one. Replace it next time with a real student error.
The reverse is informative too. Most of the class going to the same wrong option may mean the topic was learned wrong rather than that the question is bad. To tell the two apart, read the stem again; if anything in it is ambiguous, the fault is yours.
How distractors are reviewed in this pool
Every question entering the pool is evaluated together with its options before publication. The check solves the question independently and compares its own answer against the marked one. A question where those disagree does not enter the pool.
The same review removes questions where two options are correct, where none is, and where the options contain one another. Several of the patterns listed above get caught at this stage.
There is also a similarity scan: questions measuring the same objective by the same route count as duplicates and get filtered, so one exam never carries two variants of the same question.
Frequently asked
- How many distractors should I write?
- One fewer than the number of options, provided every one rests on a real student error. A distractor written as filler makes the question easier and keeps the option count only on paper.
- Why are all of the above and none of the above a problem?
- A student who sees two correct options can pick all of the above without knowing the topic. The reverse happens too: spotting one clearly wrong option rules it out. Either way the question measures elimination rather than knowledge.
- How close should distractors be?
- Close enough that a student who knows the topic can tell them apart and one who half knows it cannot. Distractors that are too close start measuring attention, and ones too far are never marked.
- Which letter should the answer be?
- No letter is preferable. It is enough that answers spread across the letters at similar rates over the whole exam. Counting the letters on the finished answer key is the fastest way to spot the imbalance.