Practice — Mild · The Five Diseases

Skills focus. Profiling · remove duplicates · Trim · true nulls · Replace Values. The lesson's cleanup, rebuilt by your own hands with the answer key beside you.

Ungraded. In-class or self-paced. Every checkpoint number below is the verified figure — if yours differs, stop and find out why before the next step.

Tasks

Import customer_export.csv via Transform Data. On the View tab, enable Column quality, Column distribution, and Column profile. Checkpoint: 514 rows; the State profile shows 30 distinct values.
Spend one minute reading profiles before fixing anything. Write down (really) the five problems you can see.
Select all columns → Remove Duplicates. Checkpoint: 500 rows.
Name column → Transform → Format → Trim. Checkpoint: no name ends in a space — spot-check by clicking a few cells and watching the value preview at the bottom left.
Segment column → replace the text N/A so those cells become true nulls. Checkpoint: the profile reports exactly 22 empty.
State column → four Replace Values steps: Texas→TX, California→CA, New York→NY, Michigan→MI. Checkpoint: 26 distinct values.
Close & Apply. Build one card: distinct count of Customer ID. Checkpoint: 500.

Hint — my Segment profile says 0 empty after replacing

Click a cell that used to say N/A and read the value preview: if it shows null in italics, you succeeded; if it shows nothing but the profile says 0 empty, you likely replaced with a space or the word null. Edit the Replaced Value step (gear icon) and make the replacement box genuinely empty.

Reflection

Which of the five diseases would have hurt a report the most if it had shipped? Rank them.
Your recipe is seven steps. How many will you have to redo when next month's file arrives?