A count is only as good as the rows behind it. If one customer appears three times, every average that includes them is wrong. Cleaning means finding these problems before you calculate.
The five problems you meet most
Problem | Example | Fix |
|---|---|---|
Duplicates | The same person entered twice | Choose a key column, remove repeats |
Inconsistent spelling | Munich, München, munich | Agree on one form and replace the others |
Extra spaces and capitals | " Anna@Example.com " | Trim spaces, compare in lower case |
Missing values | An empty country field | Fill it from another source, or mark it unknown |
Wrong types | 12,5 stored as text | Convert to a number with a point |
Which problem is it?
Duplicate
Inconsistent spelling
Missing value
In which order?
Trim and normalise first, then remove duplicates: two rows that differ only in a space are only found once the spaces are gone. Try it with the contact list worksheet and the free CSV Deduplicator.