MLB model parlays · parlay · 2026-09-09
product of 2 qualifying legs — same EV as the singles, compounded variance; exists to accrue the record
The bar is the edge: the gap between what the model thought this outcome was worth and what the exchange was asking for it. A ticket is only issued when that gap clears 5¢ after costs — the exchange spread, and a 1¢ haircut on Polymarket quotes because roughly 30% of them are already stale by the time we could act on one.
Model
22.6%
Paid
16¢
Edge
+6.3¢
Stake
18.7u
Full Kelly is growth-optimal only if the edge estimate is exactly right; overestimating it by 2× makes full Kelly growth-negative, which is easily done. Quarter Kelly keeps roughly 55% of the maximum log-growth and never lost more than half the bankroll across 2,000 simulated paths.
| Leg | Model | Price | Edge | Result |
|---|---|---|---|---|
| TEX moneyline @ 0.42TEX @ SEA | 52% | 42¢ | +10.1¢ | pending |
| WSH moneyline @ 0.37WSH @ SD | 43% | 37¢ | +6.4¢ | pending |
A parlay’s price is the product of its legs, and so is its probability — on an exchange there is no parlay juice to beat, so the expected value is identical to betting the legs separately with the variance compounded. These exist to accrue a multi-leg record honestly, not because they should win.
Not the same question as “did it win”. A bet at 38% loses nearly two times in three when it is priced perfectly, so a loss is not evidence of a mistake and a win is not evidence of skill. The closing price is the better judge — it is the market’s final answer, and it is calibrated almost perfectly.
Wrong price, no result.
The market closed at 16¢ against the 16¢ we paid — it moved −0.0¢ away from us. That is evidence the price we took was not cheap The ticket was voided before it could resolve, so this judges the price and nothing else.
Voided — stake returned, no result recorded.
ledger: starter scratch: Cal Quantrill → Cody Bradford A void is not a loss and not a win; it is removed from the record rather than counted as either, because a ticket whose premise disappeared never tested anything. The row stays visible so the void cannot quietly improve the record.
Four features, each a difference between the two sides, each oriented so a bigger number favours the home team. They are standardised, weighted, summed, and squashed into a probability.
away starter ERA − home starter ERA
away WHIP − home WHIP
home runs scored/g − away runs scored/g
away runs allowed/g − home runs allowed/g
Published 2026-09-07. Each feature is standardised to the training mean and spread, multiplied by its weight, summed with an intercept of 0.132, and squashed through a logistic into a probability. Note what the fit actually learned: the starter ERA edge — the number a human would lead with — carries a weight near zero, and team offense carries the most. The model is not the story a fan would tell about a pitching matchup.
These are the live weights, not the ones frozen at this ticket’s issue time — the ratings behind them advance with every game, so the exact feature values this ticket saw are not recoverable. The stored 22.6% above point-in-time; the weight shape below is what the model looks like today.
No evidence favors parlays on an exchange — no parlay juice to avoid; same EV as the singles with compounded variance (BET-VETTING.md §5). Exists to accrue a multi-leg record honestly, not because it should win.
tier: shadow
