Definition
A probability model is a system that estimates how often an outcome should happen. In sports betting, it turns inputs such as team strength, player availability, pace, matchup data, and market price into an estimated win probability.
The key math is expected value:
EV = (model probability x profit if win) - (loss probability x stake)
If the model probability is higher than the break-even probability from the odds, the bet has positive expected value.
Worked Example
A sportsbook lists Team A at -110. At -110, the bettor risks $110 to win $100.
Break-even probability:
110 / (110 + 100) = 52.38%
A probability model gives Team A a 56% chance to win.
Expected value on a $110 stake:
(0.56 x $100) - (0.44 x $110) = $56 - $48.40 = $7.60
The model says the bet is worth $7.60 in expected value per $110 risked, before limits, variance, and execution issues.
Why It Matters
A probability model helps a bettor compare their own estimated odds against the sportsbook price. It is most useful when it turns opinion into a number that can be checked against break-even probability.