Expected value is an average concept
Expected value combines possible outcomes, their estimated probabilities and their returns. A positive estimate does not mean the next event will win.
Real sports probabilities are not known with certainty. Model error can easily turn an apparent edge into no edge.
Small probability errors matter
When the difference between model and market is narrow, a small calibration error, missing injury or stale price can reverse the conclusion.
Use uncertainty bands and require stronger evidence than a single point estimate.
Backtests need protection against overfitting
A strategy designed around past results may capture noise. Separate training and testing periods, include all observations and account for changing market conditions.
Do not advertise a historical hit rate without odds, sample size, selection rules and maximum drawdown.
There is no risk-free value betting
Even a well-calibrated estimate experiences losing sequences and uncertainty. Financial commitments should never be based on a promised return.
If gambling is legal where you live and you choose to participate, use a fixed entertainment budget and stop before losses create pressure.