A value far from the rest of a collection can be an error, an unusual but real event, or a clue that several different groups have been mixed. Its appearance alone does not settle the explanation.
Inspect the original record and the method that produced it. Check units, entry rules, and surrounding observations. Avoid removing a value solely because the chart becomes tidier without it.
If a value is excluded for a justified reason, record the rule and consider how the result changes with it included. An unusual observation becomes useful when the investigation is transparent enough for someone else to understand the decision.
An example to consider.
Imagine one file showing a surprisingly large size. Check whether it contains a different kind of material before treating the value as a mistake.
Put it in perspective.
Treat an unexpected value as the start of an investigation. Its source and context matter before you decide whether to remove it or build a story around it.
- Inspect the source and measurement method.
- Check units and entry rules.
- Document any exclusion and its effect.
Follow a related question
Record the purpose of an important dependency.
Dependencies with a reasonName the activity the tool should improve.
New tools, familiar human questionsKeep learning
Related background to continue exploring this subject.
W3C: a primer for tabular data RFC Editor: the CSV format
