← ACARA Digital Technologies Years 7–8

Keeping a cleaning log

A record of each data problem found, the fix applied and how many rows were affected, so every change, including deleted rows, can be explained and checked.

Part of: ACARA Digital Technologies Years 7–8 — Acquiring and Storing Data — Module 73

Understanding Keeping a cleaning log in ACARA Digital Technologies Years 7–8

What it does: The Fix part of a cleaning log says what action was taken, here the TRIM function, so the change can be explained and repeated. Deleting rows removes data for good, so the log notes the problem, the fix (deleted) and the number of rows, which lets someone confirm nothing was lost by mistake. A cleaning log is a record of what you changed and why, so anyone can check your work. The log doesn't restore rows. It explains the change so the results can be trusted and checked. Rows affected counts only the rows that the fix actually changed. A problem says what was wrong. A fix says what you did about it.

Common mistakes: Line 1 should name the problem found, so it must start with 'Problem:'. 'Fix:' is for the action taken, and the next line already gives the fix. Correct line: Problem: 3 duplicate rows. COUNTA counts cells that are filled in, not blank ones. To count the blank cells (the rows affected) use =COUNTBLANK(B2:B31).

Class: _____________________  ·  Name: _____________________  ·  Date: _________

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This module's key terms are also in a printable crossword (Modules 261–300) and word search (Modules 261–324).

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Learning
Duo
What is the main purpose of a cleaning log?
To record each problem found and the fix applied, so changes can be explained and checkedTo store the final charts and graphs made from the data
Matches
Log: Fixed some data. Rows affected: ?
↓
The entry does not name the problem or the fix and gives no row count, so it cannot be checked.
Applying
Meanings
Term
cleaning log
Meaning
A record of each data problem found, the fix applied and how many rows were affected, so every change, including deleted rows, can be explained and checked.
Practice
Problem: Ava appears twice in the marks table
Testing
Gaps
Problem,Fix,
Check Answer
Spots
1Fix: 3 duplicate rows
2Fix: removed the extra copies

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Quick Questions

1. What is the main purpose of a cleaning log?
A. To record each problem found and the fix applied, so changes can be explained and checked ✓
B. To store the final charts and graphs made from the data
A cleaning log is a record of what you changed and why, so anyone can check your work.
2. Which set of columns would a useful cleaning log have?
A. Problem, Fix, Rows affected ✓
B. Name, Age, Favourite colour
A log lists the problem found, the fix applied and how many rows were affected. It is not the data itself.
3. A student finds 4 blank cells in the Age column and fills them with 'Unknown'. Which log entry is best?
A. Problem: fixed some stuff | Fix: cleaned | Rows affected: a few
B. Problem: blank Age cells | Fix: filled with 'Unknown' | Rows affected: 4 ✓
Good log entries are specific. They name the problem, describe the exact fix and give the number of rows.
4. You delete 3 duplicate rows from a survey spreadsheet. What should you do?
A. Record the deletion in the cleaning log, including that 3 rows were removed ✓
B. Nothing, because deleted rows are gone so they don't need to be recorded
Deleted rows are recorded so people know the data changed. Without a record, the missing rows can't be explained or checked.
5. Why is it important to record deleted rows in a cleaning log?
A. So the deleted rows come back automatically
B. So others can see why the row count dropped and check the deletion was fair ✓
The log doesn't restore rows. It explains the change so the results can be trusted and checked.

Match the Pairs

Problem: 3 blank Age cells → Describes the data problem that was found in the dataset
Rows affected: 12 → Shows how many rows were changed or removed by the fix
A log entry records the fix applied, so others know exactly what was done to the data → Fix: used TRIM to remove extra spaces from column B
Deleted rows must be recorded in the log, with the reason, so the change can be checked later → Problem: duplicate names | Fix: deleted rows | Rows affected: 4
Log: Fixed some data. Rows affected: ? → The entry does not name the problem or the fix and gives no row count, so it cannot be checked.
Problem: duplicates | Fix: deleted | Rows affected: 0 → Rows were deleted but the log says 0 rows were affected, so the record is wrong and hides the lost data.

Key Term

cleaning log
A record of each data problem found, the fix applied and how many rows were affected, so every change, including deleted rows, can be explained and checked.

Fill in the Blanks

1. Problem,Fix,Rows affected Blank age,Added N/A,4
Hint: Type the third column heading, which says how many rows each fix changed.
2. Total rows affected in the log: =SUM(C2:C6)
Hint: Type the function name that adds up all the numbers in the rows-affected column.
3. Problem: blank cells in column B =COUNTIF(B2:B30,"")
Hint: Type the function that counts cells matching a condition, to find how many rows to record in the log.
4. C4 holds the deleted rows from the log =COUNTA(A2:A30)+C4
Hint: Type the operator that adds the logged deleted rows back to the rows left, to check the original row count.
5. Problem: extra spaces in names Fix: =TRIM(A2)
Hint: Type the function name that removes extra spaces, which is the fix to write in the log.

Spot the Error

Question 1
A Fix: 3 duplicate rows
B Fix: removed the extra copies
C Rows affected: 3
D Deleted rows: 3 (recorded)
Line A — Line 1 should name the problem found, so it must start with 'Problem:'. 'Fix:' is for the action taken, and the next line already gives the fix. Correct line: Problem: 3 duplicate rows.
Question 2
A Rows: =COUNTA(B2:B31)
B Problem: blank Age cells
C Fix: filled with the median
D Log it in CleaningLog sheet
Line A — COUNTA counts cells that are filled in, not blank ones. To count the blank cells (the rows affected) use =COUNTBLANK(B2:B31).
Question 3
A Problem: Sidney typed 6 times
B Fix: Replace with Sydney
C Rows affected: 2
D Deleted rows: 0
Line C — The problem says Sidney was typed 6 times and Replace changed each one, so 6 rows were affected. A log with the wrong count can't be checked. It should say Rows affected: 6.
Question 4
A Problem: 5 test rows in data
B Fix: deleted rows 12 to 18
C Rows affected: 5
D Deleted rows noted in the log
Line B — Rows 12 to 18 is 7 rows, but only 5 test rows were found and the log says 5 rows were affected. The fix should say rows 12 to 16 so the log matches.
Question 5
A Problem: 4 dates typed as text
B Fix: converted to real dates
C Deleted rows: 4
D Rows affected: 4
Line C — Converting text to dates changes the cells but removes no rows. The log should say Deleted rows: 0. Rows affected is a different number from rows deleted.

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