Avoid information leakage in a backtest

A backtest can look strong when it accidentally uses information from the future. Examples include final injury status, closing prices or revised statistics that were unavailable at the chosen decision time. Build the time boundary into the dataset before evaluating results.

Work through it

1. Choose the decision timestamp and preserve the inputs available then. Keep later corrections and final outcomes in separate fields.
2. Reserve a held-out period before tuning the model. Record the experiments so the best-looking result is not presented as the only one tried.
3. Evaluate the locked method on the held-out data. Include missing-data cases and realistic availability constraints rather than dropping inconvenient events afterward.

Check your result

• Each input has an availability time.
• The test period was held out.
• Excluded events and reasons are recorded.