A mistake log is a table where every error gets a cause, not just a correction. After a few weeks the causes repeat, and the repeated cause is what you revise, not the topic.
This matters most if your results are inconsistent: you follow examples in class but lose marks when the numbers change. A log shows whether those marks are leaking from many places or from one or two habits.
Why does correcting answers not stop the same error?
Copying the right answer fixes that question. It does not name the habit that produced the wrong answer, so the habit walks into the next question unchanged.
A useful log asks four things about each error: what did I write, where exactly did it go wrong, why did my pen do that, and what would prove I have fixed it?
How to build the log, step by step
- Record the question and your wrong line, not only the right answer.
- Mark the exact step where the answer first went wrong. Often it is the second line, not the last.
- Write the cause in your own words, specific enough to act on.
- Write the correct step beside it.
- Add a retest question with different numbers, and date it. Leave the result column empty until you try it.
- After six to ten rows, group rows with similar causes and count them.
Our mistake log template gives you this layout ready to print.
Worked example: six algebra errors in two weeks
| # | Question | What I wrote | Correct | Cause |
|---|---|---|---|---|
| 1 | Expand −3(2x − 5) | −6x − 15 | −6x + 15 | Minus outside the bracket not applied to the second term |
| 2 | Simplify 4 − (x + 3) | 4 − x + 3 | 1 − x | Same: the minus reached only the first term |
| 3 | Solve 7 − 2x = 1 | x = −3 | x = 3 | Divided −6 by −2 and kept a negative |
| 4 | Expand (x − 4)² | x² − 16 | x² − 8x + 16 | Squared each term, skipped the middle term |
| 5 | Simplify 2(x − 1) − (x − 5) | x − 7 | x + 3 | Minus outside the bracket not applied to the second term |
| 6 | Area of a rectangle 6 by 4.5 | 27 | 27 cm² | Left out the unit |
Check row 5: 2(x − 1) = 2x − 2, and −(x − 5) = −x + 5, so the sum is x + 3. The student’s x − 7 comes from writing −2 − 5.
Grouping: rows 1, 2 and 5 share one cause, a minus sign outside a bracket that stops after the first term. Row 3 is a sign slip of a different kind. Rows 4 and 6 are isolated.
This is the pattern: three of six errors, all from one habit. Revising “algebra” would be too wide. Revising what a minus sign in front of a bracket does to every term inside is small enough to fix in an evening.
Retest questions for the main pattern (new numbers, same habit):
- Expand −2(3y − 7). Answer: −6y + 14.
- Simplify 10 − (2x − 3). Answer: 13 − 2x.
The mistake to avoid
The common trap is a log that grows into a diary of everything. The student writes thirty rows, each with “careless” as the cause, and never groups them.
The fix is to cap the log at one subject for two weeks and to force a specific cause on every row. If you cannot name the cause, write “cause unknown” and bring that row to a teacher or classmate. Unknown causes are useful information.
Check yourself
1. A student writes 5 − (2x − 1) = 5 − 2x − 1. Name the cause in one sentence, then write the correct line.
Show answer
The minus outside the bracket was applied to 2x but not to the −1. The correct line is 5 − 2x + 1 = 6 − 2x.
2. Three log rows have the causes “forgot to convert minutes to hours”, “used cm with m in one formula” and “left out the unit”. Do they form one pattern? If so, name it.
Show answer
Yes. All three are unit handling.
The pattern could be named “units not checked before and after”. ” at the start of each question addresses it.
3. After a retest, row 1 scores correct, but only when the question is the same shape. What should the next retest change?
Show answer
Change the shape, for example put the bracket in the middle of a longer expression. One correct retest with the same shape does not show the habit has gone. Retesting without repeating the same numbers explains how to vary a question safely.
Where this leads next
Once you have a named pattern, practise it with a short mixed set so the skill has to be chosen, not just repeated. The original mixed-practice builder helps you assemble that set, and moving from following an example to choosing a method covers the next skill.
You can find the pattern yourself in most cases. A one-to-one teacher becomes worth considering when the pattern is clear in the log but returns whenever you work alone, because a teacher can see your pen in real time and ask why you wrote a line.
That is the kind of work we do in online one-to-one Mathematics tuition, and the paid trial is the place to test whether it helps. More routes are listed under learning routes for students.