send-experiment-designer

# Send Experiment Designer Designs email experiments across four modes and reads them out: a falsifiable hypothesis, a variant matrix that isolates **one** variable per cell, a sample-size / minimum-detectable-effect / run-duration / power plan, and a documented effect/uncertainty read. It may apply an owner-approved precommitted action rule, but statistical output alone never chooses a business action. **Mode set (pick one):** | Mode | Isolated variable | Primary metric | |------|-------------------|----------------| | `a-b` | one change — subject *or* preheader *or* CTA *or* creative | open (subject) / click / CTOR (CTA/creative) | | `multivariate` | 2+ factors crossed (e.g. subject × CTA), one variable per cell | the goal metric, powered per cell | | `send-time` | deploy hour/day; subject, segment, creative held constant | same-window engagement (open/click) | | `hold-out` | send vs no-send (randomized control receives nothing / current default) | conversion or revenue-per-recipient (incremental lift) | Default the mode from the request when it is unambiguous (e.g. "test two subject lines" → `a-b`, "best hour to send" → `send-time`, "measure incremental revenue" → `hold-out`); state the picked mode back and proceed. **Scope guard:** this skill owns email **experiment design + the significance read** only. It scores the SEND **E (Engagement)** lever as a test signal — it does **not** compute the profile-weighted **EQS** or run the `S1/S2/N1/D1` vetoes ([email-quality-a...