Bubble Sheet Grading FAQ

No. Your PDF never leaves your computer. All grading — reading the bubbles, scoring, building the marked PDF and the CSV — happens inside your browser, on your own device. There is no upload step, no server, no third party.

Your scanned PDFs and page images are never stored. For guests and free accounts, results stay in the browser unless you download them yourself. Premium scan history stores the small structured data needed to rebuild a CSV: the answer key, each student's responses, and scores. It keeps the latest 50 scans, and you can delete entries.

Reading bubbles, scoring, and building downloads all happen on your own device. Your scanned pages are not sent to a server or third party. Premium history is a separate feature that stores structured results, not scans; account details and messages you send through Contact are also stored.

No. Grading works without signing in, with unlimited use and unlimited marked-PDF downloads. An account adds the class statistics (mean, median, min, max) for free, and Premium adds the full analysis and history.

No. Sheets can be scanned sideways, upside down, or slightly skewed. Every sheet has four corner markers — three squares and one circle — and the circle anchors the orientation. The reader uses all four markers to mathematically straighten the page before reading it, so bubbles land exactly where the sheet geometry says they should.

Use dark pencil and fill bubbles completely. The reader measures how dark the inside of each bubble is, so light or partial marks may not read. A standard #2 pencil filled solid always reads.

Yes. On the answer key (page 1), shade every acceptable letter. Any of them counts as correct for every student.

Blank pages are skipped. A student sheet that doesn't match the answer key's sheet code (for example a 50-question sheet in a 20-question class run) is listed as not graded rather than scored wrongly. Unrecognized pages are listed too.

Place the completed answer key as page 1 of the PDF, followed by all student answer sheets. Use our printable answer sheets, export or scan the whole stack into one PDF, then grade the PDF in your browser.

The class score summary. Mean is the average score. Median is the middle score when everyone is ranked — half scored above it, half below. Minimum and Maximum are the lowest and highest scores.

How spread out the scores are around the mean, in points. A small number means the class scored similarly; a large number means scores ranged widely. Calculated as the square root of the average squared distance from the mean.

A consistency score from 0 to 1 for the whole test. It asks: would students who score high on half the questions also score high on the other half? Built from each question's difficulty (p×(1−p)) compared against the total score variance. Rated Good (0.80+), Acceptable (0.70+), Fair (0.50+), or Low.

How many points a student's score could plausibly wobble on a re-test, derived from the spread of scores and the reliability. A score of 17 ± 1 means the student's true ability likely sits between 16 and 18.

Per question: the share of students who answered correctly. 0.85 means 85% got it right. Despite the name, higher = easier.

Per question: how well getting this question right tracks the overall score. It correlates each student's right/wrong on the question with their total score minus that question, so it can't inflate itself. Positive means stronger students got it right more often — what a good question does. Negative is a red flag.

A simpler per-question check: split the class into the top 27% and bottom 27% by total score, then subtract the lower group's success rate from the upper group's. Near 0 or negative means the question doesn't separate strong from weak students.

Per question: how many students picked each option, left it blank, or shaded more than one bubble. This shows whether a wrong option is genuinely tempting (a good distractor) or dead weight that nobody picks.

Questions are flagged when the numbers above suggest a problem: Possible wrong key (top scorers mostly chose a different letter than the key), Negative discrimination (stronger students did worse), Low discrimination, Very hard (under 25% correct), or Everyone correct (the question isn't telling you anything).

A pairing check for copying. Two students are flagged when they share an unusually high number of identical wrong answers — wrong in the same way, not just the same score. Two students can score 12/20 independently; only matching wrong letters on enough questions (at least 10% of the test and 75% of one student's wrong answers) raises a flag. It's an indicator to look into, not proof.

When you download the marked PDF with Premium, the analysis is appended as a final page (or two) after the marked answer sheets — the same numbers shown on screen, in print form for your records.

Guests (no account) and free accounts can both grade unlimited scans and download marked PDFs. Signing in (free) adds the class statistics: mean, median, min, max. Premium ($10 one time — not a subscription) adds the full question analysis, reliability, answer similarity, the report page in the marked PDF, CSV export, and the last-50 scan history.

No. It's $10, once, per account. No renewals, no recurring charges.