Three layers of metrics
Delivery metrics (impressions, CTR) describe what the media did. Cost metrics (CPI, CPA) describe efficiency. Outcome metrics (conversion rate, retention, ROAS analysis, LTV signals) describe whether it was worth doing.
Reporting that mixes all three without hierarchy tends to obscure the decision. Lead with the outcome layer and use the others to explain it.
Cohorts over snapshots
Mobile value accrues over time. Comparing cohorts by acquisition week gives a far more reliable read than comparing calendar-month totals, particularly when spend levels change.
Agree the definitions
Most measurement disputes are definitional. Writing down what counts as a conversion, which window applies, and which source naming is authoritative prevents them.