Example
order_id is unique in the clean retail file; campaign plus period is the marketing key.
Check your understanding
Write your own example from a current course. Explain what could go wrong if this concept were ignored. Compare the population, time boundary and units to the case definition.
Make the reasoning yours.
Try the activity before reading its reference. Keep your sources, commands and assumptions with your work. Companion activities are unsaved self-practice and do not award a certificate or change lesson progress.