A repeatable Excel data analysis process

Step 1 — Profile before you calculate

• Row and column counts, and whether they match the source
• Per column: type, blanks, unique values, min, max, average
• Duplicates on whatever should be a key

Step 2 — Fix quality, then freeze it

Clean in one pass and keep the raw data on a separate sheet. If someone questions a number later, you need to be able to show the original.

Step 3 — Aggregate at the grain of the decision

Weekly decisions need weekly aggregates. Analysing daily data for a monthly decision manufactures noise and invites over-reaction.

Step 4 — Always compare

• Previous period, same period last year, plan or target
• Segment against the total, not against another segment
• State the baseline in the sentence, not just in the chart

Step 5 — Write findings, not observations

"Revenue rose 8%" is an observation. "Revenue rose 8%, driven by the East region's 21% increase, while West declined 3%" is a finding a reader can act on.