Peer-reviewed empiricalEvidence: StrongAdvanced4 min summary
David Winkelmann, Marius Ötting, Christian Deutscher, Tomasz Makarewicz · 2024 · Journal of Sports Economics
Apparent inefficiencies appear in individual seasons but do not persist systematically across seasons or leagues, and simulations show that significant single-season results are likely even in a fully efficient market.
Does not show: That no bettor can ever find an edge; it shows that single-season evidence is weak.
Used in: The Edge Is in the Price, Not in Picking the Winner · A Profitable Backtest That Never Existed · Lesson 5 · +5 more
Peer-reviewed replicationEvidence: StrongIntermediate4 min summary
Lawrence Clegg, John Cartlidge · 2025 · International Journal of Forecasting
Much of the original out-of-sample profit depended on a single outlier bet recorded at erroneously long odds; after correction only one strategy remained significantly profitable in the original period, returns came mainly from individual bookmakers' mispricing rather than the buzz signal, and there were no further profits in data after 2020.
Does not show: That attention-based signals never contain information; it shows this published profit was not robust.
Used in: A Profitable Backtest That Never Existed · Lesson 5 · Lesson 6 · +4 more
Peer-reviewed empiricalEvidence: LimitedIntermediate4 min summary
Conor Walsh, Alok Joshi · 2024 · Machine Learning with Applications
Selecting models by calibration produced better simulated betting outcomes than selecting by accuracy. After the 2025 corrigendum, average returns were negative for both selection rules (about −9.8% for calibration versus −26.8% for accuracy), while the best single models reached about +23.1% and +10.9%.
Does not show: That calibrated models are profitable; the corrected average returns were negative.
Correction: Corrigendum, Machine Learning with Applications 19 (2025), 100627 (doi:10.1016/j.mlwa.2025.100627). The original 2024 return figures were withdrawn; use the corrected values.
Used in: Kelly, Drawdowns and the Danger of a Confident Forecast · Lesson 18 · Lesson 23 · +1 more
Peer-reviewed methodsEvidence: ModerateExpert3 min summary
Tadgh Hegarty, Karl Whelan · 2024 · Sports Economics Review
Tests based on normalised probabilities behave well; tests based on raw inverse odds do not, and are biased against finding a favourite–longshot bias.
Does not show: Any profitable strategy; it shows how test design can change conclusions.
Used in: A Profitable Backtest That Never Existed · Lesson 2 · Lesson 11 · +1 more
Peer-reviewed methodsEvidence: StrongIntermediate2 min summary
Glenn W. Brier · 1950 · Monthly Weather Review
Introduces what is now called the Brier score, which rewards forecasts that are both well calibrated and sharp.
Does not show: Whether a forecast can make money against a market.
Used in: Lesson 18 · Lesson 23
Peer-reviewed theoryEvidence: StrongAdvanced3 min summary
David H. Bailey, Jonathan M. Borwein, Marcos López de Prado, Qiji Jim Zhu · 2014 · Notices of the American Mathematical Society
With enough trials, an impressive in-sample backtest is likely even when no strategy has skill, and overfit strategies tend to perform worse out of sample.
Does not show: That every strong backtest is overfit; it shows why the number of trials must be reported.
Used in: A Profitable Backtest That Never Existed · Lesson 12 · Lesson 19 · +3 more
Peer-reviewed empiricalEvidence: LimitedIntermediate2 min summary
Philip Ramirez, J. James Reade, Carl Singleton · 2023 · International Journal of Forecasting
Reported that attention-related signals were associated with mispricing and profitable strategies; later corrected by Clegg & Cartlidge.
Does not show: A durable profitable strategy, once the outlier bet is corrected.
Used in: A Profitable Backtest That Never Existed · Lesson 21