# Benchmark protocol v0.2.0

## Benchmark layers
1. **Original-valid layer**: clinically/reference-valid QA before empirical evidence gating.
2. **Evidence-gated primary layer**: items that pass clinician evidence sufficiency and pre-registered empirical dependence criteria.
3. **Adversarial/safety layer**: question-only, hard mismatch, wrong organ/modality, and blank/occluded conditions.

## Why these layers are separate
Combining them into a single score hides mechanism. A model can answer original items well while ignoring images, or use images well but fail to abstain when the evidence is invalid.

## Ranking analysis
For every frozen model panel, compute rankings on original-valid and evidence-gated layers. Report Spearman rho, Kendall tau, absolute rank displacement, pairwise inversions, and item-clustered bootstrap confidence intervals. Pair inversion is an informative secondary result, not a required outcome.

## Item-first reporting
Report item-level condition scores and distributions, not only aggregate accuracy. Stratify by question family, answer type, modality, label frequency and doctor evidence state.

## Pilot limitation
The current four-case package cannot support research-grade ranking inference. All evidence-audit files are schemas/templates until a sufficiently large frozen set exists.