Offer timing and efficacy of benefits: Design an experiment to test whether a bonus (e.g., cash or queue priority) increases the share of paperwork-complete candidates who complete their first action within 14 days. Specify eligibility/exclusions; unit of randomization; treatment arms (control, bonus-now, bonus-after-first-action, staged bonus); stratification to separate bonus-dependent vs. intrinsically motivated users; primary/secondary metrics and guardrails (quality, fraud, downstream retention); handling noncompliance, spillovers, and interference; stopping rules and decision criteria. Compute the minimum per-arm sample size to detect a +3 percentage-point lift from a 20% baseline at 90% power, α=0.05 using a two-proportion z-test—show formula and a numeric result. Explain when to roll out benefits broadly vs. target narrowly based on heterogeneous treatment effects.