Backtest

The structure of walk-forward analysis, the metrics it produces (IS-OOS gap, parameter stability), a momentum-lookback tuning case, and the limits that keep it from being a universal validator.

Concrete cases of look-ahead bias and survivorship bias — full-period momentum normalization, financial disclosure lag, close-on-close fills, S&P 500 reconstitution, the limits of free APIs — followed by an avoidance checklist.

Covers the formulas and interpretation of CAGR, MDD, Sharpe Ratio, and other backtest metrics, plus five common backtesting pitfalls.