Model versus market, and model versus line
Three different quantities: what the market thinks is fair, what a price needs to break even, and what a bet returns on average. Plus what the product shows when no reference exists.
Most confusion about prop research comes from three numbers that look alike and mean different things. The product keeps them apart and labels every one of them.
The market estimate
When sportsbooks quote both sides of a market, the two implied probabilities add up to more than one. The excess is the book's margin. Removing it proportionally leaves a fair probability, which is the market's own opinion with its margin stripped out. The product labels this Market estimate and only shows it when a displayable reference exists at the same line the app posts.
Break-even at this price
Break-even is a different question: what share of decided outcomes does this specific price need in order to come out level? It is computed from the posted price on this side alone, never from a de-vigged fair. At -110 the fair is 50.0% while the break-even is 52.381%, and treating the first as the second is how a 51% estimate reads as an edge when it is not one.
A model probability of 51% at a posted -110 clears the fair by one point and misses the break-even by 1.381 points. The expected net return is negative 2.64% per unit staked.
Expected net return
Expected net return combines the win probability, the loss probability and the push probability with the price. A push is refunded rather than counted as a loss, and the three probabilities must sum to one or the calculation is refused rather than approximated.
The labels the product uses
- Market estimate: a de-vigged sportsbook consensus at this line.
- Break-even at this price: derived from the price the app published on this side.
- Break-even at this payout: derived from a stated payout multiplier rather than odds.
- Estimated goblin break-even: a screening assumption for a reduced payout product whose multiplier the app does not publish.
- Model estimate: the simulation's own probability.
Model versus line
Most sports have no sportsbook player prop reference at all. Football player props are not posted by sharp books in a comparable form, and a probe of tennis found match odds only. In those sports the product says model versus line and shows no market edge, because inventing one would be fabricating the market's opinion.
Related
Slateline is an educational research and analysis product. It does not place bets or accept wagers. Projections are estimates, not guarantees. If gambling stops being fun, call 1 800 GAMBLER.