COUNCIL RULING: MLB Player Props Model Anchor Methodology Date: 2026-04-03 Ruled by: Boss (Ernest)

DECISIONS:

1. Career data source: MLB Stats API (free). Pull career totals per player.
2. Execution threshold: Tier C (track only) for now. Data collection phase - no executable edges. Will reassess when sample accumulates.
3. H2H threshold: 30 PA minimum, max 20% weight. Below 30 PA use pitcher archetype matching.
4. Kalshi microstructure: Not building into edge calc now. Boss will evaluate liquidity/spreads manually.
5. Career prior: MLB Stats API career stats as primary. Steamer/ZiPS for rookies later if needed.

KEY METHODOLOGY ADOPTED:

• Per-PA rates (not per-game) as foundation
• Bayesian shrinkage with research-backed k values (HR=170PA, K=60PA, BABIP=800+PA)
• Log-Odds opponent adjustment
• Gaussian copula for HRR correlation
• Two-component NegBin mixture for Pitcher Outs
• 3-year handedness-specific park factors
• Pitcher archetypes for opponent matching (below 30 PA H2H)
• Dual-anchor tracking with DM test + mSPRT
• Confidence tier system (currently Tier C)

DEFERRED:

• Ridge regression betas (need training data)
• Monte Carlo RBI/Runs simulation
• Spring training data integration
• Steamer/ZiPS projection integration