Keeping an Error Log
Most students who plateau below the qualifying line are not missing knowledge. They are repeating the same three or four mistakes. The error log exists to make those patterns visible.
The one rule
Every wrong answer and every "blank I could have done" gets a row, written the same day, with a cause from this list:
| Cause | Meaning | Typical fix |
|---|---|---|
| concept | You did not know the fact or method | Read the topic page; do 5 easier problems on that leaf |
| careless | Knew it, executed badly: arithmetic slip, sign error, dropped a case | Slow down on the final step; write the answer as a full sentence before bubbling |
| misread | Solved a different problem (wrong quantity, "not", "distinct", "at least", units) | Underline the question's last sentence; re-read before answering |
| time | Ran out of time or abandoned it | Check the 4-minute rule; practice that band under time |
| trap | Fell for the problem's designed wrong answer | Read the "Common mistakes" for the problem; look for the trap next time |
The site's error log (Errors page) stores this for you and exports a CSV. On paper, the template is:
| Date | Problem | Topic | Cause | What I should have noticed | Re-attempt on |
|---|
The column that matters is "What I should have noticed". Write it as an instruction to yourself for next time, not a description of the error:
- Bad: "forgot the case where the digit is 0."
- Good: "when counting digit strings, ask first whether 0 is allowed in each position."
Weekly review (20 minutes, day 7)
- Sort the week's rows by cause. The largest group is your priority for next week, whatever the topic.
- If careless + misread are more than a third of the rows, your next timed test is about checking, not about new problems: budget 5 minutes at the end for re-reading 1–10.
- If concept rows cluster in one leaf, move that leaf to the top of the next topic cycle.
- Re-attempt every row from two weeks ago without looking at the solution. Anything still wrong gets a second row and a note about why the first fix did not stick.
The review schedule the site uses
A missed problem comes back after 1, 3, 7 and 14 days. A correct solve in a review session advances it; a miss resets it to day 1. Four correct reviews retire it. Keep the queue under about 15 problems; if it grows past that, you are attempting too many new problems for the amount of review you are doing.