Model
GSSM — runs scored/surrendered model. OLS of the actual home run margin on four home/away team averages, converted to a win probability and then calibrated on the model's own out-of-sample history. Multiple models share this machine, differing only in what feeds the four averages:
- runs — actual runs for/against (the baseline).
- xwoba — Statcast expected offense (team xwOBA) instead of actual runs.
E[home margin] = b₀ + b₁·GFH(home) + b₂·GAH(home) + b₃·GFA(away) + b₄·GAA(away)
P(home win) = P( N(E[margin], SE) > 0 ), SE = √(SSE / (n−2))
Each model refits nightly on all final games of the season (minimum 60). Predictions are stored pre-game and scored out-of-sample as results arrive — the Accuracy page compares the models honestly.
Fit history
| Fitted (UTC) | Model | Games | b₀ | GFH | GAH | GFA | GAA | SE | In-sample acc | Brier |
|---|---|---|---|---|---|---|---|---|---|---|
| 2026-07-30 02:04 | xwoba | 1619 | -0.599 | 1.009 | -2.633 | 6.022 | -2.453 | 4.631 | 52.3% | 0.249 |
| 2026-07-30 02:04 | runs | 1619 | -0.662 | 1.172 | -1.095 | -1.090 | 1.150 | 4.515 | 57.6% | 0.241 |
| 2026-07-30 02:01 | runs | 1619 | -0.662 | 1.172 | -1.095 | -1.090 | 1.150 | 4.515 | 57.6% | 0.241 |
| 2026-07-30 01:54 | runs | 1619 | -0.662 | 1.172 | -1.095 | -1.090 | 1.150 | 4.515 | 57.6% | 0.241 |