STAGE 1: Ask an answerable question
Concept: A business question needs a measure and scope.
Task: Define net sales, reporting period and format categories before opening a chart.
Acceptance: Explain how refunds and missing values will be treated.

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STAGE 2: Clean with a record
Concept: Cleaning decisions should be reversible and auditable.
Task: Preserve raw data and create a change log for labels, duplicates and invalid values.
Acceptance: Never silently discard inconvenient rows.

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STAGE 3: Analyze and reconcile
Concept: A grouped result should tie back to source totals.
Task: Compute gross sales, refunds and net sales by format in SQL or a spreadsheet.
Acceptance: Check totals using an independent calculation.

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STAGE 4: Communicate uncertainty
Concept: A chart is evidence for a decision, not a substitute for context.
Task: Write a one-page recommendation with one chart and two limitations.
Acceptance: Do not imply profitability when only revenue data are available.

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