/power-analysis — Power / MDE for study design

Compute the three interlocking quantities of an ex-ante design calculation — power, required N, and minimum detectable effect (MDE) — and emit a power section the user can paste straight into a preregistration. Analytical for standard designs; simulation-based (reusing the /simulation-study harness pattern) for non-standard ones.

Core principle: a power calculation is a design-time commitment made before the data exist. Fix any two of {effect size, N, power} and solve for the third; never back out a "power" number from a realised estimate (that is post-hoc power, and it is uninformative — see "What this skill does NOT do").

When to use

• Before launching an RCT / field / survey experiment — to choose N (or clusters) for a target MDE at 80–90% power.
• Invoked by /preregister for RCTs — the AEA RCT Registry and most IRBs require a power/MDE justification; /preregister's aea-rct style calls this skill to fill that section.
• During R&R — when a referee asks "was this study adequately powered to detect the effect you claim?"
• Designing a Monte Carlo — to set R and sample sizes before handing off to /simulation-study.

Inputs

$ARGUMENTS may carry flags; missing pieces are elicited in Phase 0.