← ACARA Digital Technologies Years 9–10

Keeping a cleaning log

A record of each change made to the data: what changed, how many rows it affected and why. It lets other people check the cleaning and repeat it.

Part of: ACARA Digital Technologies Years 9–10 — Acquiring and Validating Data — Module 109, QCE Digital Solutions Unit 4 — Complex Digital Data Exchange Problems and Solution Requirements — Module 74

Understanding Keeping a cleaning log in ACARA Digital Technologies Years 9–10

What it does: Stating the count lets someone compare the data before and after to confirm the change was done correctly. Naming the step, the tool and the column gives enough detail for someone else to repeat the cleaning and get the same result. A good entry says what changed, how many rows were affected and why. Vague entries like 'tidied up' can't be checked or repeated. A cleaning log is a record of the changes. It makes the cleaning checkable and repeatable, and it doesn't shrink the file. Logging each change as you make it keeps the record accurate. Memory fades and steps get missed, so the cleaning can't be repeated.

Common mistakes: The log numbers do not add up. 120 - 18 = 102, not 112. The log should say 8 rows were removed so the before and after counts match. The reason does not match the change. Trimming spaces is done so names match, not to delete outliers. A log reason must explain the change that was actually made.

Class: _____________________ · Name: _____________________ · Date: _________

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This module's key terms are also in a printable crossword (Modules 333–377) and word search (Modules 333–412).

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Each concept is reinforced from every angle — learned, then applied, then tested.

Learning

Duo

Which log entry is better for a cleaning log?

Tidied up the data a bitRemoved 6 duplicate rows because the same survey was submitted twice

Matches

Log: Fixed some data

↓

Too vague: it does not say what changed, how many rows were affected or why

Applying

Meanings

Term

cleaning log

Meaning

A record of each change made to the data: what changed, how many rows it affected and why. It lets other people check the cleaning and repeat it.

Practice

Change: Trimmed spaces in Name column

Testing

Gaps

CREATE TABLE CleaningLog (why );

Check Answer

Spots

1Rows before: 120

2Rows removed: 18

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Quick Questions

1. Which log entry is better for a cleaning log?

A. Removed 6 duplicate rows because the same survey was submitted twice ✓

B. Tidied up the data a bit

A good entry says what changed, how many rows were affected and why. Vague entries like 'tidied up' can't be checked or repeated.

2. What is the main purpose of a cleaning log?

A. So others can check the cleaning and repeat it ✓

B. So the dataset takes up less storage space

A cleaning log is a record of the changes. It makes the cleaning checkable and repeatable, and it doesn't shrink the file.

3. Which detail tells a reader how many rows were affected?

A. Replaced 'Vic' with 'VIC' in some rows

B. Replaced 'Vic' with 'VIC' in 14 rows ✓

The sub-theme 'how many rows affected' needs an actual number. 'Some rows' doesn't let anyone check your work.

4. When should you write a cleaning log entry?

A. Only once at the end, from memory

B. Straight after making each change ✓

Logging each change as you make it keeps the record accurate. Memory fades and steps get missed, so the cleaning can't be repeated.

5. Which entry gives the reason for a change?

A. Deleted 3 rows with no age because age is needed for the research question ✓

B. Deleted 3 rows with no age

The 'why' explains the decision. Without it, another person can't judge whether the change was sensible.

Match the Pairs

Row 14: Changed 'Vic.' to 'VIC' (6 rows) → A cleaning log entry that records what changed and how many rows were affected

Reason: Removed duplicate survey entries → The 'why' part of a cleaning log entry, explaining the purpose of the change

A log entry should show how many rows were affected, so the change can be checked → Deleted blank rows: 12 rows affected

A cleaning log lets another person repeat the cleaning in the same steps → Step 3: TRIM applied to column B (names), 40 rows

Log: Fixed some data → Too vague: it does not say what changed, how many rows were affected or why

Cleaned the data, then wrote the log a week later from memory → The log was not recorded as each change was made, so details may be forgotten or wrong

Key Term

cleaning log

A record of each change made to the data: what changed, how many rows it affected and why. It lets other people check the cleaning and repeat it.

Fill in the Blanks

1. CREATE TABLE CleaningLog (why TEXT);

Hint: Type the data type used for words, such as the reason for a change.

2. INSERT INTO CleaningLog VALUES ('Trim', 12);

Hint: Type the SQL keyword that introduces the data for the new log entry.

3. =COUNTIF(B2:B101,"N/A")

Hint: Type the spreadsheet function that counts matching cells, so you can log how many rows were affected.

4. SELECT SUM(rowsAffected) FROM CleaningLog;

Hint: Type the function that adds up the rows affected across every logged change.

5. SELECT why FROM CleaningLog;

Hint: Type the column name that holds the reason for each change.

Spot the Error

Question 1

A Rows before: 120

B Rows removed: 18

C Rows after: 112

Line B — The log numbers do not add up. 120 - 18 = 102, not 112. The log should say 8 rows were removed so the before and after counts match.

Question 2

A Change: trimmed Name spaces

B Rows affected: 14

C Reason: to delete outliers

Line C — The reason does not match the change. Trimming spaces is done so names match, not to delete outliers. A log reason must explain the change that was actually made.

Question 3

A Change: removed 9 duplicates

B Rows affected: 5

C Reason: stop double counting

Line A — The change says 9 duplicates but 'Rows affected' says 5. A log must be consistent. The change line should say 5 duplicates.

Question 4

A Step,Change,Rows

B 1,Trim names,14,Fix spacing

C 2,Remove blanks,6,Missing data

Line A — The header is missing the Reason column, but each row has four values. A cleaning log needs what changed, rows affected and why, so the header should be Step,Change,Rows,Reason.

Question 5

A SET log TO empty list

B REMOVE blank rows

C ADD 'Cleaned data' TO log

D SAVE log WITH the data

Line C — The log entry is too vague. It must say what changed and how many rows were affected, for example 'Cut 6 blank rows'. Otherwise nobody can check or repeat the step.

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