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Apply a ship rule to a test: signup lift with a refund guardrail

  • For Product managers
  • You practice Catching mistakes and made-up facts
  • Time about 5 minutes
  • Level Advanced

About this exercise

Your team's rule for the new pricing page test is to ship only if signups rise by at least 5% relative and the refund rate (refunds divided by signups) doesn't get worse by more than 1 percentage point. Write a prompt for exactly 3 plain-text lines: "Lift:" with the relative signup lift shown with its numbers, "Guardrail:" with both refund rates and the difference, and "Decision:" Ship or Don't ship plus a reason under 12 words. Under 80 words.

Common mistakes when you ask AI for this

  • Shipping on the lift alone. The AI follows the excited lead and ignores refunds. Try: Say: "Ship only if both conditions pass; the refund rate is a guardrail."
  • Dividing by visitors for refunds. Refund rate uses signups, not visitors. Try: Say: "Refund rate = refunds / signups."
  • Skipping the numbers. A verdict without math can't be checked. Try: Say: "Show the numbers on each line."
  • Letting markdown through. AI adds bold text and headings by default. Try: Add: "Plain text only, no bold, no headings."
  • Trusting the AI to count words. AI is bad at counting and often runs past a word limit. Try: Cap each part (for example "each line under 15 words") so the total lands well under the limit.

What a strong prompt includes

  • Names the three labels
  • States the refund formula
  • Requires both conditions
  • Shows numbers
  • Caps reason and length

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