Derived Columns Without Overwriting Evidence

Unit ID: M09-U05 Estimated active time: 20-30 minutes

A derived column records a transparent calculation from existing fields.

clean["hours"] = clean["minutes"] / 60
clean["passed_score"] = clean["score"].ge(70).fillna(False)

Do not replace minutes with hours when both are useful. Keep the original cleaned field and use a new name with a unit.

Document the formula, inputs, missing-value rule, and purpose. A derived value does not create new evidence beyond its source fields.

Practice: create completed_and_passed using status and score. Explain why a missing score produces False under this course rule.