Find the question that was wrong, not just hard
Two numbers for every item on your test, from the marks you have already entered. Difficulty says how many got it right. Discrimination says whether the learners who understood the topic did better on it than the ones who did not — and when the answer is no, the item is usually miskeyed.
The sample includes an item whose answer key turned out to be wrong — no account needed.
What the two numbers mean
They answer different questions, and only one of them tells you whether to throw an item away.
Difficulty (p) — and the name is backwards
The share of learners who got it right, so a high p is an easy item. On its own it says little: an item everyone passes and an item everyone fails are equally uninformative.
Discrimination (D) — the one that matters
Split the class by total score into the strongest and weakest papers, then ask whether the strong group got this item right more often. If they did not, the item is not measuring what the rest of the test measures.
A negative D is usually a wrong key
If the weak group did better than the strong group, something is wrong with the item — and by far the most common something is that the answer key is wrong. That one check is worth the whole exercise. No amount of staring at the paper finds it.
Which wrong answer they chose
A tally per option, so you can see whether a distractor pulled everybody or nobody. An option no learner picks is not testing anything and is worth rewriting before the next paper.
How the groups are split, and why it changes for a small class
The statistic is only as trustworthy as the two groups it compares.
The upper and lower 27%
Taking the extreme 27% at each end maximises the gap between the groups while keeping each one big enough to mean something. That is the whole reason for the odd-looking fraction — it is Kelley’s, and it assumes a reasonably large group.
Under 30 papers, halves instead
For a class of twelve, 27% is three papers, and three papers is noise — one absent learner would swing every D on the sheet by a third. Below 30 the class is split in half, which is the usual classroom practice and keeps each group worth reading. The sheet prints which basis it used.
See it on a real paper
A 20-item Grade 7 Science test, marked, with every item scored on both measures.
Including the miskeyed item
The whole sheet: difficulty, discrimination, the verdict per item, and the distractor tallies behind it.
Open the sample testBefore the testTable of Specifications
Build the paper from your topics and the days taught, with an item column that sums exactly.
See the TOS generatorEverything elseGrades, forms, attendance
Class records to DO 015 s. 2026, report cards that print finished, and the SF2 register.
See all the featuresRun it on a test you have already marked
The marks are the only input. If you have entered a test, the analysis is already available.