03 · Practise and check
Try this yourself
Design a cleaning log with columns for row ID, original value, new value and reason. Apply it to five fictional rows.
Check your understanding
Two records from the same city are not duplicates merely because their city field matches. Duplicate rules depend on what one row represents.
A mistake to avoid
If cleaning uses learned statistics such as means, fit those statistics on training data only and apply them unchanged to validation and test data.
Before looking at the answer, write a short explanation and one example of your own. Finish by naming one limitation of the method. Use Mark as read when you are ready, or return to the previous lesson if a term is unclear.
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