Retail · Excel
Duplicate customer validation and coincidental name-match quantification
Independent grading: 88/100(verify, opens in a new tab)
Problem
Chidi Okafor at Meridian Retail (simulated retailer) needed to validate whether the system's duplicate flag was reliable, and to quantify how many name matches in the data were genuine duplicates versus different people who happened to share a name.
What I did
On the Customers sheet, I added a Name Match Count column using COUNTIF on the Full Name column, then applied conditional formatting to highlight any row where that count exceeded one. A Verified Duplicate column combines the name-match condition with the is_duplicate flag using a logical AND, marking only records that both methods agree on. The Duplicate Summary sheet presents five metrics built from COUNTIF and COUNTIFS formulas, and each metric row includes the actual formula expression in a methodology column so Chidi's team can audit the logic directly. A KPI card row at the top of the sheet lets an investor scan the five headline numbers without reading the table detail.
Finding
All 200 system-flagged duplicates are confirmed by the name-pattern method, a 100% detection rate, while 240 additional name matches are coincidental and do not represent true duplicates.
Outcome
Chidi received an investor-grade due diligence sheet that validated the duplicate detection system and clearly separated genuine duplicates from coincidental name overlaps, both with transparent formula evidence.
Next step
Reviewing the 240 coincidental name matches for shared addresses or email domains would determine whether any should be reclassified as genuine duplicates the system missed.
- COUNTIF for single-condition counts
- COUNTIFS for multi-condition counts
- Conditional formatting with formula-based rules
- Structured summary table layout for non-technical audiences
- Reconciliation bridge formulas linking multiple count methodologies