Conciseness

The body is mostly lean and assumes competence (e.g., it names 'Two-proportion z-test' and 'Mann-Whitney U' without explaining them), but the decision-ownership rule is restated in the intro, Skill Contract, step 7, and Next Best Skill, which is trimmable repetition. It sits above the 'mostly efficient with some unnecessary explanation' anchor but short of 'every token earns its place'.

Actionability

Concrete, executable guidance includes the copy-paste-ready helper invocation ('python3 "${CLAUDE_PLUGIN_ROOT}/scripts/connectors/experiment.py" proportion --control <conv> <n> ...'), a fill-in hypothesis template, and a specific data-source table. It falls short of the fully-executable anchor because the 'continuous' and 'samplesize' subcommands and the bootstrap/Mann-Whitney paths are named but never exemplified.

Workflow Clarity

Nine numbered steps are clearly sequenced (mode → hypothesis → matrix → metrics → sizing → significance → decision ownership → provenance → binding verification) with explicit checkpoints: the NEEDS_INPUT gate in step 1, the precommitment decision gate in step 7, and the binding-refusal rule in step 9, plus a 'Done when' checklist. Error/recovery paths are explicit rather than implicit, matching the top anchor.

Progressive Disclosure

Good structure with well-signaled, one-level-deep references — both referenced local bundle files (references/test-design-guide.md, references/measurement-control.md) exist — and a dedicated Reference Materials section. It falls short of the top anchor because some statistical detail in step 6 is inlined where the guide file would serve, and several references point outside the skill bundle to files that cannot be verified from it.

Specificity

The description lists multiple concrete deliverables — 'produces a hypothesis, variant matrix, sample-size/duration/power plan, and a documented effect/uncertainty read from own exported results' — covering the skill's full capability range. It exceeds the 'several specific actions with minor gaps' anchor, matching the comprehensive anchor instead.

Completeness

It explicitly answers 'when' with concrete quoted trigger phrases ('Use when the user asks to...') and 'what' with the full deliverable list, plus negative boundaries. This matches the anchor requiring both what and when with concrete triggers, rather than the merely-adequate anchor.

Trigger Term Quality

Quoted natural trigger phrases like '"design an A/B test"', '"set up a creative/landing test"', and '"run an incrementality test"' mirror what users would actually say. It falls short of the comprehensive anchor because common synonyms such as 'split test', 'A/B/n', or 'experiment' are not included as triggers.

Distinctiveness Conflict Risk

Explicit exclusions — 'Not for producing variants — use ad-creative-builder; not for reading back one shipped change — use paid-measurement-loop' — carve out a clear niche with minimal conflict risk. It is clearly distinct from adjacent measurement/creative skills, matching the clear-niche anchor.