Playbook: A/B Test Rewarded vs Interstitial Sources for the Same Goal

Playbook: A/B Test Rewarded vs Interstitial Sources for the Same Goal

Same budget, two formats — pick with data, not folklore:
— Split equal spend across rewarded and interstitial, same geo and audience
— Hold creative concept constant; only the format and placement differ
— Measure install volume AND day-7 retention separately per format
— Expect rewarded to win on volume/CPI but lose on early retention
— Check event depth: rewarded users often complete fewer real in-app actions
— Compute cost-per-retained-user, not cost-per-install, as the deciding metric
— Run long enough to see retention, not just the install spike

✓ Settles the rewarded-vs-interstitial debate with your own data
✓ Cost-per-retained-user cuts through the CPI mirage
✗ Rewarded's volume advantage tempts the wrong call on CPI alone
✗ Needs a retention window, so it's not a same-day answer

Verdict: Use rewarded for cheap top-of-funnel volume, interstitial when retained-user cost matters more than install count.
Best for: Buyers choosing between in-app ad formats for a single KPI.