Hypothesis: Store B is cheaper. Feelings agree. Receipts might not.

Materials

• One locked weekly basket from recent line items, not a fantasy meal plan
• Up to three stores you can actually reach this week
• Paid prices from your receipts where you have them
• Fees you will really pay (delivery, membership amortized)

Method

1. Freeze the list. No swapping items mid-test to rescue a favorite store.
2. Price the same SKUs across stores. Fill gaps carefully; capture next trip to tighten them.
3. Add fees to the total that will actually leave the bank account.
4. Read the winner in dollars. Re-run next month, since prices move.

Sample result

Locked list: $118.40 at Store A, $109.10 at Store B, $102.55 at the club before fees. Amortize the club fee across trips you will take. Store B may win a normal Tuesday even when two club stickers looked louder.

Allowed exceptions

Produce wins at A, pantry at B. Split only if the dollar gap beats time and impulse risk. Meat, diapers, specialty diets, and bulk oils often flip the race. Note which SKUs decide the winner so next month's test starts smarter.

Conclusion format

Write one sentence: "This week Store ___ wins this basket by $___." Feelings can still choose convenience. They no longer get to invent the math.